Optical sheet member and image display device using same

ABSTRACT

An optical sheet member includes a polarizing plate including a polarizer (A); an optical conversion member (D); and a brightness enhancement film including a reflection polarizer (B), wherein the brightness enhancement film has a reflection center wavelength range of 300 nm to 430, and the optical conversion member (D) converts a part or all of UV light which is transmitted through polarizer (B) and is incident on the optical conversion member (D), and has an emission center wavelength range of 300 nm to 430 nm and which has an emission center wavelength range of 430 nm to 480 nm, green light which has an emission center wavelength range of 500 nm to 600 nm, and red light which has an emission center wavelength range of 600 nm to 700 nm.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Divisional of U.S. patent application Ser.No. 14/959,466, filed on Dec. 4, 2015, which is a Continuation of PCTInternational Application No. PCT/JP2014/065121, filed on Jun. 6, 2014,which was published under PCT Article 21(2) in Japanese, and whichclaims priority under 35 U.S.C. Section 119(a) to Japanese PatentApplication No. 2013-119670 filed on Jun. 6, 2013. The aboveapplications are hereby expressly incorporated by reference, in theirentirety, into the present application.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an optical sheet member and an imagedisplay device employing the same.

2. Description of the Related Art

A flat panel display such as a liquid crystal display device(hereinafter, also referred to as an LCD) has been widely used as animage display device having small power consumption and space savingproperties over the years. The liquid crystal display device has aconfiguration in which backlight (hereinafter, also referred to as BL),a backlight side polarizing plate, a liquid crystal cell, a visible sidepolarizing plate, and the like are disposed in this order.

In the recent flat panel display market, development for power saving,high definition, and color reproducibility improvement has progressed asan LCD performance enhancement, and currently, power saving, highdefinition, and color reproducibility improvement have been remarkablyrequired in a small-size device, particularly for example, a tablet PCor a smart phone, but development of next generation high vision (4K2K,an EBU ratio of greater than or equal to 100%) of current TV standards(FHD, National Television System Committee (NTSC) ratio of 72% EuropeanBroadcasting Union (EBU) ratio of 100%) has progressed in a large-sizedevice. For this reason, the power saving, the high definition, and thecolor reproducibility improvement of the liquid crystal display devicehave been increasingly required.

An optical sheet member is disposed between the backlight and thebacklight side polarizing plate according to power saving of thebacklight, and the optical sheet member is an optical device in which,among incident light rays while vibrating in all directions, only lightrays vibrating in a specific polarization direction are transmitted, andlight rays vibrating in the other polarization direction are reflected.As a core component of a low power LCD according to an increase in amobile device and low power consumption in a home electric appliance,improvement of light efficiency of the LCD and an increase in brightness(a degree of brightness per unit area of a light source) have beenexpected.

In response, a technology has been known in which an optical sheetmember (a Dual Brightness Enhancement Film (DBEF) or the like) iscombined between the backlight and the backlight side polarizing plate,and thus a light utilization rate of the BL is improved according tooptical recycling, and the brightness is improved while saving power ofthe backlight (refer to JP3448626B). Similarly, in JP1989-133003A(JP-H01-133003A), a technology is disclosed in which a light utilizationrate of the BL is improved in the optical recycling according tobroadband in a polarizing plate having a configuration in which a λ/4plate and a cholesteric liquid crystalline phase are laminated and alayer formed by fixing cholesteric liquid crystalline phases of three ormore layers having different pitches are laminated and a layer formed byfixing cholesteric liquid crystalline phases of three or more layershaving different pitches of the cholesteric liquid crystalline phases.

However, such an optical sheet member has a complicated memberconfiguration, and thus it is necessary to reduce the cost by reducingthe number of members in which functions of the members are furtherintegrated in order to spread the optical sheet member to the market.

On the other hand, a method has been known in which a light emittingspectrum of the backlight is sharpened from a viewpoint of highdefinition of a liquid crystal display device and of improving colorreproducibility thereof. For example, in JP2012-169271A, a method isdisclosed in which white light is realized by using a quantum dot (QD)emitting red light and green light as a fluorescent body between a blueLED and a light guide plate, and thus high brightness and an improvementin color reproducibility are realized. In SID'12 DIGEST p.895, a methodis proposed in which an optical conversion sheet using a quantum dot(QDEF, also referred to as a quantum dot sheet) is combined in order toenhance color reproducibility of the LCD.

SUMMARY OF THE INVENTION

In JP3448626B and JP1989-133003A (JP-H01-133003A) in which a lightutilization rate is enhanced, a broadband optical recycling function isapplied to the white light, and thus the design is complicated inconsideration of a multilayer configuration and wavelength dispersionproperties of the member, and manufacturing costs are high. In addition,in a fluorescent (PL) application technology disclosed in JP2012-169271Aand SID'12 DIGEST p.895, high brightness and an improvement in colorreproducibility are realized according to the white light by using theQuantum Dot (hereinafter, also referred to as a QD), but it is necessaryto be combined with JP3448626B and JP1989-133003A (JP-H01-133003A) inorder to further enhance the brightness, and thus the same problems asdescribed above occur.

The enhancement in a BL light utilization rate necessary for powersaving and high definition (a decrease in an opening ratio) and animprovement in color reproducibility (a decrease in transmittance of acolor filter (hereinafter, also referred to as a CF)) have a trade-offrelationship, and it is necessary to make the enhancement in the lightutilization rate and the color reproducibility compatible. In addition,an object of the present invention is to reduce the cost by reducing thenumber of members in which functions of the members are furtherintegrated, to reduce a film thickness of the member by integrating themembers or to reduce interface reflection loss at an air layer of a gapbetween the members, and to eliminate a display defect due to foreignsubstances mixed between the members, which is likely to occur at thetime of manufacturing a display device or after manufacturing thedisplay device.

An object of the present invention is to provide an optical sheet memberin which front brightness, front contrast, and a color reproducingregion are enhanced and color unevenness in an inclined azimuth is alsoable to be reduced by thinning or integrating members at the time ofbeing incorporated in an image display device using UV narrowband or Bnarrowband backlight.

In order to attain the object described above, as a result of intensivestudies of the present inventors, it has been found that a lightutilization rate is increased by using a reflection polarizer whichfunctions as a backlight light source unit having a wavelength region ofmonochromatic bright line light (a half-value width of less than orequal to 100 nm, for example, a blue light source in 430 nm to 470 nm,and for example, a B-LED at 465 nm) having a narrow emission peak in a Bwavelength region and an UV light source (an UV-LED having an emissionspectrum in 300 nm to 430 nm, and the like) having a narrow emissionpeak in an UV wavelength region and has a narrow reflection peak, andoptical conversion is performed by using a quantum dot (includingquantum effect particles such as quantum dot particles, quantum rodparticles, and quantum tetrapod particles) or a PL material (an organicmaterial and an inorganic material), and thus it is possible toconcurrently improve front brightness, front contrast, and a colorreproducing region, and to reduce color unevenness in an inclineddirection with a simple configuration, and it is possible to attain theobject described above.

That is, the object described above is attained by the present inventionhaving the following configuration.

[1] An optical sheet member including a polarizing plate including apolarizer (A); an optical conversion member (D); and a brightnessenhancement film including a reflection polarizer (B), in which thebrightness enhancement film has a reflection center wavelength in awavelength range of 400 nm to 500 nm and a peak of reflectivity having ahalf-value width of less than or equal to 100 nm, and the opticalconversion member (D) converts a part of blue light which is transmittedthrough the reflection polarizer (B) and is incident on the opticalconversion member (D), and has an emission center wavelength in thewavelength range of 400 nm to 500 nm and a peak of emission intensityhaving a half-value width of less than or equal to 100 nm into greenlight which has an emission center wavelength in a wavelength range of500 nm to 600 nm and a peak of emission intensity having a half-valuewidth of less than or equal to 100 nm and red light which has anemission center wavelength in a wavelength range of 600 nm to 700 nm anda peak of emission intensity having a half-value width of less than orequal to 100 nm, and transmits a part of the blue light.

[2] In the optical sheet member according to [1], it is preferable thatthe brightness enhancement film has a reflection center wavelength in awavelength range of 430 nm to 480 nm and has a peak of reflectivityhaving a half-value width of less than or equal to 100 nm, and theoptical conversion member (D) converts a part of blue light which istransmitted through the reflection polarizer (B) and is incident on theoptical conversion member (D), and has an emission center wavelength inthe wavelength range of 430 nm to 480 nm and a peak of emissionintensity having a half-value width of less than or equal to 100 nm intogreen light which has an emission center wavelength in the wavelengthrange of 500 nm to 600 nm and a peak of emission intensity having ahalf-value width of less than or equal to 100 nm and red light which hasan emission center wavelength in a wavelength range of 600 nm to 650 nmand a peak of emission intensity having a half-value width of less thanor equal to 100 nm, and transmits a part of the blue light.

[3] An optical sheet member including a polarizing plate including apolarizer (A); an optical conversion member (D); and a brightnessenhancement film including a reflection polarizer (B), in which thebrightness enhancement film has a reflection center wavelength in awavelength range of 300 nm to 430 nm and a peak of reflectivity having ahalf-value width of less than or equal to 100 nm, and the opticalconversion member (D) converts a part or all of UV light which istransmitted through the reflection polarizer (B) and is incident on theoptical conversion member (D), and has an emission center wavelength inthe wavelength range of 300 nm to 430 nm and a peak of emissionintensity having a half-value width of less than or equal to 100 nm intoblue light which has an emission center wavelength in a wavelength rangeof 430 nm to 480 nm and a peak of emission intensity having a half-valuewidth of less than or equal to 100 nm, green light which has an emissioncenter wavelength in a wavelength range of 500 nm to 600 nm and a peakof emission intensity having a half-value width of less than or equal to100 nm, and red light which has an emission center wavelength in awavelength range of 600 nm to 700 nm and a peak of emission intensityhaving a half-value width of less than or equal to 100 nm.

[4] In the optical sheet member according to [3], it is preferable thatthe optical conversion member (D) converts a part or all of UV lightwhich is transmitted through the reflection polarizer (B) and isincident on the optical conversion member (D), and has an emissioncenter wavelength in the wavelength range of 300 nm to 430 nm and a peakof emission intensity having a half-value width of less than or equal to100 nm into blue light which has an emission center wavelength in thewavelength range of 430 nm to 480 nm and a peak of emission intensityhaving a half-value width of less than or equal to 100 nm, green lightwhich has an emission center wavelength in the wavelength range of 500nm to 600 nm and a peak of emission intensity having a half-value widthof less than or equal to 100 nm, and red light which has an emissioncenter wavelength in a wavelength range of 600 nm to 650 nm and a peakof emission intensity having a half-value width of less than or equal to100 nm.

[5] In the optical sheet member according to [1], it is preferable thatthe reflection polarizer (B) includes a first light reflecting layerwhich has a reflection center wavelength in the wavelength range of 400nm to 500 nm and a peak of reflectivity having a half-value width ofless than or equal to 100 nm, and is formed by fixing a cholestericliquid crystalline phase, and the brightness enhancement film includes aλ/4 plate (C) satisfying Expression (1) described below between thepolarizer (A) and the reflection polarizer (B). Further, a wavelengthdispersion of the λ/4 plate (C) may be a forward dispersion“Re(450)>Re(550)”, and as the wavelength dispersion of the λ/4 plate(C), a flat dispersion “Re(450)≅Re(550)” is able to be preferably used,and a reverse dispersion “Re(450)<Re(550)” is able to be is morepreferably used.

450 nm/4−60 nm<Re(450)<450 nm/4+60 nm  Expression (1)

(In Expression (1), Re(λ) represents retardation in an in-planedirection at a wavelength of λ nm, and unit is nm.)

[6] In the optical sheet member according to any one of [1], [2], and[5], it is preferable that the reflection polarizer (B) includes a firstlight reflecting layer which has a reflection center wavelength in thewavelength range of 430 nm to 480 nm and a peak of reflectivity having ahalf-value width of less than or equal to 100 nm, and is formed byfixing the cholesteric liquid crystalline phase, and the brightnessenhancement film includes the λ/4 plate (C) satisfying Expression (1′)described below between the polarizer (A) and the reflection polarizer(B).

Expression (1′) 450 nm/4 - 25 nm <Re(450)<450 nm/4 +25 nm In Expression(1′), Re(λ) represents retardation in an in-plane direction at awavelength of λ nm, and unit is nm.

[7] In the optical sheet member according to [1], it is preferable thatthe reflection polarizer (B) is a dielectric multilayer film which has areflection center wavelength in the wavelength range of 400 nm to 500 nmand a peak of reflectivity having a half-value width of less than orequal to 100 nm.

[8] In the optical sheet member according to [3] or [4], it ispreferable that the reflection polarizer (B) includes a first lightreflecting layer which has a reflection center wavelength in thewavelength range of 300 nm to 430 nm and a peak of reflectivity having ahalf-value width of less than or equal to 100 nm, and is formed byfixing a cholesteric liquid crystalline phase, and the brightnessenhancement film includes a λ/4 plate (C) satisfying Expression (2)described below between the optical conversion member (D) and thereflection polarizer (B). Further, a wavelength dispersion of the λ/4plate (C) may be a forward dispersion “Re(380)>Re(450)”, and as thewavelength dispersion of the λ/4 plate (C), a flat dispersion“Re(380)≅Re(450)” is able to be preferably used, and a reversedispersion “Re(380)<Re(450)” is able to be more preferably used.

Expression (2) 380 nm/4−60 nm<Re(380)<380 nm/4+60 nm

(In Expression (2), Re(λ) represents retardation in an in-planedirection at a wavelength of λ nm, and unit is nm.)

[9] In the optical sheet member according to any one of [3], [4], and[8], it is preferable that the reflection polarizer (B) includes thefirst light reflecting layer which has a reflection center wavelength inthe wavelength range of 300 nm to 430 nm and a peak of reflectivityhaving a half-value width of less than or equal to 100 nm, and is formedby fixing the cholesteric liquid crystalline phase, and the brightnessenhancement film includes the λ/4 plate (C) satisfying Expression (2′)described below between the optical conversion member (D) and thereflection polarizer (B).

380 nm/4−25 nm <Re(380)<380 nm/4+25 nm  Expression (2′)

In Expression (2′), Re(λ) represents retardation in an in-planedirection at a wavelength of λ nm, and unit is nm.

[10] In the optical sheet member according to [3] or [4], it ispreferable that the reflection polarizer (B) is a dielectric multilayerfilm which has a reflection center wavelength in the wavelength range of300 nm to 430 nm and a peak of reflectivity having a half-value width ofless than or equal to 100 nm.

[11] In the optical sheet member according to any one of [1] to [10], itis preferable that the optical conversion member (D) and the reflectionpolarizer (B) are laminated in direct contact with each other or throughan adhesive layer.

[12] In the optical sheet member according to any one of [5], [6], [8],and [9], it is preferable that the polarizing plate, the opticalconversion member (D), the 214 plate (C), and the reflection polarizer(B) are sequentially laminated in direct contact with each other orthrough an adhesive layer.

[13] In the optical sheet member according to any one of [1] to [12], itis preferable that a difference in refractive indexes between thereflection polarizer (B) and a layer in direct contact with thereflection polarizer (B) on the polarizing plate side is less than orequal to 0.15.

[14] In the optical sheet member according to any one of [1] to [13], itis preferable that a film thickness of the brightness enhancement filmis 3 pm to 10 pm.

[15] In the optical sheet member according to [1] or [2], it ispreferable that the optical conversion member (D) includes a fluorescentmaterial emitting the green light and the red light when the blue lightis incident thereon.

[16] In the optical sheet member according to [3] or [4], it ispreferable that the optical conversion member (D) includes a fluorescentmaterial emitting the blue light, the green light, and the red lightwhen light having an emission center wavelength in the wavelength rangeof 300 nm to 430 nm and a peak of emission intensity having a half-valuewidth of less than or equal to 100 nm is incident thereon.

[17] In the optical sheet member according to [15] or [16], it ispreferable that the optical conversion member (D) is a thermoplasticfilm which is formed by being stretched after dispersing quantum dotsheets, quantum rods, or quantum dot materials, or an adhesive layer onwhich quantum rods or quantum dot materials are dispersed.

[18] In the optical sheet member according to any one of [1] to [17], itis preferable that the optical conversion member emits fluorescent lightholding at least a part of polarization properties of an incidence ray.

[19] In the optical sheet member according to [18], it is preferablethat, in the optical conversion member, a polarization degree offluorescent light emitted from the optical conversion member is 10% to99% when light having a polarization degree of 99.9% is incident on theoptical conversion member.

[20] In the optical sheet member according to any one of [1] to [19], itis preferable that the optical conversion member includes a fluorescentmaterial in which light exited from the optical conversion memberincludes the linear polarization light and circular polarization light.

[21] In the optical sheet member according to any one of [1] to [20], itis preferable that light exited from the optical conversion memberincludes the linear polarization light, and the polarizing plate furtherincludes a linear polarization reflection polarizer or further includesa linear polarization reflection polarizer between the polarizing plateand the optical conversion member.

[22] In the optical sheet member according to [21], it is preferablethat the linear polarization reflection polarizer is a dielectricmultilayer film which reflects at least a part of light in a wavelengthrange of 300 nm to 500 nm.

[23] In the optical sheet member according to [21], it is preferablethat the linear polarization reflection polarizer is a linearpolarization reflection polarizer including a λ/4 plate on both sides ofa light reflecting layer which is formed by fixing a cholesteric liquidcrystalline phase reflecting at least a part of light in a wavelengthrange of 300 nm to 500 nm.

[24] In the optical sheet member according to any one of [1] to [20], itis preferable that light exited from the optical conversion memberincludes the circular polarization light, and the polarizing platefurther includes a circular polarization reflection polarizer or furtherincludes a circular polarization reflection polarizer between thepolarizing plate and the optical conversion member.

[25] In the optical sheet member according to [24], it is preferablethat the circular polarization reflection polarizer is a circularpolarization reflection polarizer including a λ/4 plate on both sides ofa dielectric multilayer film which reflects at least a part of light ina wavelength range of 300 nm to 500 nm.

[26] In the optical sheet member according to [24], it is preferablethat the circular polarization reflection polarizer is a circularpolarization reflection polarizer including a light reflecting layerwhich is formed by fixing a cholesteric liquid crystalline phasereflecting at least a part of light in a wavelength range of 300 nm to500 nm and a λ/4 plate which is arranged between the light reflectinglayer and the polarizing plate.

[27] In the optical sheet member according to any one of [1] to [26], itis preferable that the optical conversion member is pattern-formed ateach two or more types of fluorescent wavelengths.

[28] An image display device including the optical sheet memberaccording to [1] or [2]; and a backlight unit, in which the backlightunit includes a light source emitting blue light which has an emissioncenter wavelength in the wavelength range of 430 nm to 480 nm and a peakof emission intensity having a half-value width of less than or equal to100 nm, and the backlight unit includes a reflection member performingconversion of a polarization state of light which is emitted from thelight source and is reflected on the optical sheet member and reflectionof the light in a rear portion of the light source.

[29] An image display device including the optical sheet memberaccording to [3] or [4]; and a backlight unit, in which the backlightunit includes a light source emitting UV light which has an emissioncenter wavelength in the wavelength range of 300 nm to 430 nm and a peakof emission intensity having a half-value width of less than or equal to100 nm, and the backlight unit includes a reflection member performingconversion of a polarization state of light which is emitted from thelight source and is reflected on the optical sheet member and reflectionof the light in a rear portion of the light source.

[30] In the image display device according to [28] or [29], it ispreferable that a difference between a wavelength applying a peak ofemission intensity of blue light or UV light of the backlight unit and awavelength applying a peak of reflectivity in the brightness enhancementfilm is 5 nm to 70 nm.

[31] In the image display device according to any one of [28] to [30],it is preferable that the image display device further includes a liquidcrystal cell.

[32] In the image display device according to [28], it is preferablethat the backlight unit includes a wavelength selective filter for ablue color which selectively transmits light having a wavelength shorterthan 480 nm among the blue light rays.

[33] In the image display device according to any one of [28] to [32],it is preferable that the image display device further includes a thinlayer transistor, and the thin layer transistor includes an oxidesemiconductor layer having a carrier concentration of less than1×10¹⁴/cm³.

According to the present invention, it is possible to provide an opticalsheet member in which the thickness of the member is thinned by reducingthe number of members, the occurrence of brightness unevenness issuppressed by foreign substances mixed into the display device, frontbrightness, front contrast, and a color reproducing region are able tobe enhanced, and color unevenness in an inclined azimuth is able to bereduced when the optical sheet member is incorporated in an imagedisplay device using UV narrowband or B narrowband backlight.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view illustrating a sectional surface of anexample of an optical sheet member of the present invention using aquantum dot material which is able to convert B into G and R as anoptical conversion member by using a layer formed by fixing a Bnarrowband cholesteric liquid crystalline phase as a reflectionpolarizer along with a positional relationship with respect tobacklight.

FIG. 2 is a schematic view illustrating a sectional surface of anotherexample of the optical sheet member of the present invention using thequantum dot material which is able to convert B into G and R as theoptical conversion member by using the layer formed by fixing the Bnarrowband cholesteric liquid crystalline phase as the reflectionpolarizer along with the positional relationship with respect to thebacklight.

FIG. 3 is a schematic view illustrating a sectional surface of stillanother example of the optical sheet member of the present inventionusing the quantum dot material which is able to convert B into G and Ras the optical conversion member by using the layer formed by fixing theB narrowband cholesteric liquid crystalline phase as the reflectionpolarizer along with the positional relationship with respect to thebacklight.

FIG. 4 is a schematic view illustrating a sectional surface of stillanother example of the optical sheet member of the present inventionusing an adhesive layer on which the quantum dot material which is ableto convert B into G and R is dispersed as the optical conversion memberby using the layer formed by fixing the B narrowband cholesteric liquidcrystalline phase as the reflection polarizer along with the positionalrelationship with respect to the backlight.

FIG. 5 is a schematic view illustrating a sectional surface of stillanother example of the optical sheet member of the present inventionusing the quantum dot material which is able to convert UV into B, G,and R as the optical conversion member by using the layer formed byfixing an UV narrowband cholesteric liquid crystalline phase as thereflection polarizer along with the positional relationship with respectto the backlight.

FIG. 6 is a schematic view illustrating a sectional surface of anexample of the optical sheet member of the present invention using aquantum dot material which is able to convert B into G and R as anoptical conversion member by using a B narrowband dielectric multilayerfilm as a reflection polarizer along with a positional relationship withrespect to backlight.

FIG. 7 is a schematic view illustrating a sectional surface of anotherexample of the optical sheet member of the present invention using thequantum dot material which is able to convert B into G and R as theoptical conversion member by using the B narrowband dielectricmultilayer film as the reflection polarizer along with the positionalrelationship with respect to the backlight.

FIG. 8 is a schematic view illustrating a sectional surface of stillanother example of the optical sheet member of the present inventionusing the quantum dot material which is able to convert B into G and Ras the optical conversion member by using the B narrowband dielectricmultilayer film as the reflection polarizer along with the positionalrelationship with respect to the backlight.

FIG. 9 is a schematic view illustrating a sectional surface of stillanother example of the optical sheet member of the present inventionusing an adhesive layer on which quantum dot materials which are able toconvert B into G and R are dispersed as the optical conversion member byusing the B narrowband dielectric multilayer film as the reflectionpolarizer along with the positional relationship with respect to thebacklight.

FIG. 10 is a schematic view illustrating a sectional surface of stillanother example of the optical sheet member of the present inventionusing a quantum dot material which is able to convert UV into B, G, andR as an optical conversion member by using a layer formed by fixing anUV narrowband dielectric multilayer film as the reflection polarizeralong with the positional relationship with respect to the backlight.

FIG. 11 is a schematic view illustrating a sectional surface of anexample of a liquid crystal display device which is an image displaydevice of the present invention.

FIG. 12 is a schematic view illustrating a preferred relationshipbetween an absorption axis direction of a backlight side polarizer and aslow axis direction of a λ/4 plate when a spiral structure of a layerformed by fixing a cholesteric liquid crystal is a right spiral.

FIG. 13 is a schematic view illustrating a preferred relationshipbetween an absorption axis direction of a backlight side polarizer and aslow axis direction of a λ/4 plate when a spiral structure of a layerformed by fixing a cholesteric liquid crystal is a left spiral.

FIG. 14-A is a schematic view illustrating a sectional surface ofanother example of the liquid crystal display device which is the imagedisplay device of the present invention.

FIG. 14-B is a schematic view illustrating a sectional surface of stillanother example of the liquid crystal display device which is the imagedisplay device of the present invention.

FIG. 15 is a schematic view illustrating a sectional surface of stillanother example of the liquid crystal display device which is the imagedisplay device of the present invention.

FIG. 16 is a schematic view illustrating a sectional surface of stillanother example of the liquid crystal display device which is the imagedisplay device of the present invention.

FIG. 17 is a schematic view illustrating a sectional surface of stillanother example of the liquid crystal display device which is the imagedisplay device of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an optical sheet member and an image display device of thepresent invention will be described in detail.

The following description of configuration requirement is based on arepresentative embodiment of the present invention, but the presentinvention is not limited to such an embodiment. Furthermore, herein, anumerical range denoted by using “to” indicates a range includingnumerical values described before and after “to” as a lower limit valueand an upper limit value.

Herein, a “half-value width” of a peak indicates the width of a peak ata peak height of ½.

[Optical Sheet Member]

A first aspect of an optical sheet member of the present inventionincludes a polarizing plate including a polarizer (A); an opticalconversion member (D); and a brightness enhancement film including areflection polarizer (B), the brightness enhancement film has areflection center wavelength in a wavelength range of 400 nm to 500 nm(preferably, in a wavelength range of 430 nm to 480 nm) and a peak ofreflectivity having a half-value width of less than or equal to 100 nm,the optical conversion member (D) converts a part of blue light which istransmitted through the reflection polarizer (B) and is incident on theoptical conversion member (D), and has an emission center wavelength ina wavelength range of 400 nm to 500 nm (preferably, in a wavelengthrange of 430 nm to 480 nm) and a peak of emission intensity having ahalf-value width of less than or equal to 100 nm into green light whichhas an emission center wavelength in a wavelength range of 500 nm to 600nm and a peak of emission intensity having a half-value width of lessthan or equal to 100 nm and red light which has an emission centerwavelength in a wavelength range of 600 nm to 700 nm (preferably, in awavelength range of 600 nm to 650 nm) and has a peak of emissionintensity having a half-value width of less than or equal to 100 nm, andtransmits a part of the blue light.

A second aspect of the optical sheet member of the present inventionincludes a polarizing plate including a polarizer (A); an opticalconversion member (D); and a brightness enhancement film including areflection polarizer (B), the brightness enhancement film has areflection center wavelength in a wavelength range of 300 nm to 430 nmand a peak of reflectivity having a half-value width of less than orequal to 100 nm, and the optical conversion member (D) converts a partor all of UV light which is transmitted through the reflection polarizer(B) and is incident on the optical conversion member (D), and has anemission center wavelength in a wavelength range of 300 nm to 430 nm anda peak of emission intensity having a half-value width of less than orequal to 100 nm into blue light which has an emission center wavelengthin a wavelength range of 430 nm to 480 nm and a peak of emissionintensity having a half-value width of less than or equal to 100 nm,green light which has an emission center wavelength in a wavelengthrange of 500 nm to 600 nm and a peak of emission intensity having ahalf-value width of less than or equal to 100 nm, and red light whichhas an emission center wavelength in a wavelength range of 600 nm to 700nm (preferably, in a wavelength range of 600 nm to 650 nm) and a peak ofemission intensity having a half-value width of less than or equal to100 nm.

According to such a configuration, in the optical sheet member of thepresent invention, the thickness of the member is thinned by reducingthe number of members, the occurrence of brightness unevenness issuppressed by foreign substances mixed into the display device, frontbrightness, front contrast, and a color reproducing region are able tobe enhanced, and color unevenness in an inclined azimuth is able to bereduced when the optical sheet member is incorporated in an imagedisplay device using backlight in which a bright line having ahalf-value width of less than or equal to 100 nm is in an UV range and abright line having a half-value width of less than or equal to 100 nm isin a B range.

In FIG. 1 to FIG. 10, a schematic view of the optical sheet member ofthe present invention is illustrated along with a backlight unit 31. Anoptical sheet member 21 of the present invention includes a polarizingplate 1 and a brightness enhancement film 11. The polarizing plate 1 andthe brightness enhancement film 11 may be laminated through an adhesivelayer 20 (refer to FIG. 1, FIG. 2, and the like), or may be separatelyarranged (refer to FIG. 3 and the like).

<Polarizing Plate>

Next, a polarizing plate will be described.

In general, the polarizing plate of the optical sheet member of thepresent invention is formed of a polarizer (A) and two polarizing plateprotective films (hereinafter, also referred to as a protective film)arranged on both sides thereof, as with a polarizing plate used in aliquid crystal display device, and in the present invention, in order tofurther reduce the thickness of the optical sheet member, it ispreferable that the protective film is further thinned (the thickness ofthe protective film is less than or equal to 40 μm, is preferably lessthan or equal to 25 μm, and is more preferably less than or equal to 15μm), it is more preferable that a hard coat formed by coating, drying,and curing a protective resin such as an acrylic resin is used (thethickness of the hard coat is less than or equal to 20 μm, is preferablyless than or equal to 10 μm, and is more preferably less than or equalto 5 μm), and it is even more preferable that a polarizer in which aprotective layer is not disposed is used for realizing a thin opticalsheet member. In the present invention, it is more preferable that aretardation film is used as the protective film arranged on the liquidcrystal cell side between the two protective films in a case of a liquidcrystal display device in a VA mode, an IPS mode, a TN mode, and an OCBmode, it is preferable that an optical compensation film which does notsubstantially have a phase difference is used in a case of a liquidcrystal display device in an IPS mode, and it is preferable that theoptical compensation film is not used for realizing a thin optical sheetmember.

In FIG. 1 to FIG. 10, the polarizing plate 1 includes a polarizer 3. Thepolarizing plate 1 may include a retardation film 2 on the surface ofthe polarizer 3 on a visible side, and the polarizing plate 1 mayinclude a polarizing plate protective film 4 on the surface of thepolarizer 3 on a backlight unit 31 side (refer to FIG. 2, FIG. 3, FIG.7, FIG. 8, and the like), or may not include the polarizing plateprotective film 3 (refer to FIG. 1, FIG. 6, and the like).

(Polarizer)

It is preferable that a polarizer in which iodine is adsorbed andaligned in a polymer film is used as the polarizer (A) described above.The polymer film described above is not particularly limited, andvarious films are able to be used as the polymer film. Examples of thepolarizer include a hydrophilic polymer film such as a polyvinylalcohol-based film, a polyethylene terephthalate-based film, an ethyleneand vinyl acetate copolymer-based film, or a partially saponified filmthereof, and a cellulose-based film, a polyene-based alignment film suchas a substance of polyvinyl alcohol subjected to a dehydration treatmentor a substance of polyvinyl chloride subjected to a dehydrochlorinationtreatment, and the like. Among them, a polyvinyl alcohol-based filmhaving excellent dyeability of iodine is preferably used as thepolarizer (A).

Polyvinyl alcohol or a derivative thereof is used as the material of thepolyvinyl alcohol-based film. Examples of the derivative of thepolyvinyl alcohol include polyvinyl formal, polyvinyl acetal, and thelike, and a substance modified with olefin such as ethylene andpropylene, an unsaturated carboxylic acid such as an acrylic acid, amethacrylic acid, and a crotonic acid and alkyl ester thereof, acrylamide, or the like.

A degree of polymerization of the polymer which is the material of thepolymer film described above is generally in a range of 500 to 10,000,is preferably in a range of 1,000 to 6,000, and is more preferably in arange of 1,400 to 4,000. Further, in a case of a saponified film, adegree of saponification, for example, is preferably greater than orequal to 75 mol %, is more preferably greater than or equal to 98 mol %,and is even more preferably 98.3 mol % to 99.8 mol %, from a viewpointof solubility with respect to water.

The polymer film (an unstretched film) described above is subjected toat least a monoaxially stretching treatment and an iodine dyeingtreatment according to a normal method. Further, a boric acid treatmentand a cleaning treatment are able to be performed. In addition, apolymer film (a stretched film) subjected to the treatments describedabove is subjected to a drying treatment according to a normal method,and thus the polarizer (A) is obtained.

A stretching method in the monoaxially stretching treatment is notparticularly limited, and both of a wet stretching method and a drystretching method are able to be adopted as the stretching method.Examples of stretching means of the dry stretching method include aninter-roll stretching method, a heating roll stretching method, acompression stretching method, and the like. The stretching is able tobe performed in multiple steps. In the stretching means described above,the unstretched film is generally in a heated state. A stretching ratioof the stretched film is able to be suitably set according to thepurpose, and the stretching ratio (the total stretching ratio) isapproximately 2 times to 8 times, is preferably 3 times to 7 times, andis more preferably 3.5 times to 6.5 times.

The iodine dyeing treatment, for example, is performed by dipping thepolymer film in an iodine solution containing iodine and potassiumiodide. The iodine solution is generally an aqueous solution of iodine,and contains iodine and potassium iodide as a dissolution aid. An iodineconcentration is approximately 0.01 mass % to 1 mass %, and ispreferably 0.02 mass % to 0.5 mass %, and a potassium iodideconcentration is approximately 0.01 mass % to 10 mass %, and ispreferably 0.02 mass % to 8 mass %.

In the iodine dyeing treatment, the temperature of the iodine solutionis generally approximately 20° C. to 50° C., and is preferably 25° C. to40° C. A dipping time is generally in a range of approximately 10seconds to 300 seconds, and is preferably in a range of 20 seconds to240 seconds. In the iodine dyeing treatment, an iodine content and apotassium content in the polymer film are adjusted to be in the rangedescribed below by adjusting conditions such as the concentration of theiodine solution, and the dipping temperature and the dipping time of thepolymer film with respect to the iodine solution. The iodine dyeingtreatment may be performed before the monoaxially stretching treatment,during the monoaxially stretching treatment, or after the monoaxiallystretching treatment.

The iodine content of the polarizer (A) described above, for example, isin a range of 2 mass % to 5 mass %, and is preferably in a range of 2mass % to 4 mass %, in consideration of optical properties.

It is preferable that the polarizer (A) described above containspotassium. A potassium content is preferably in a range of 0.2 mass % to0.9 mass %, and is more preferably in a range of 0.5 mass % to 0.8 mass%. The polarizer (A) contains the potassium, and thus it is possible toobtain a polarization film having a preferred composite modulus (Er) anda high polarization degree. The potassium is able to be contained, forexample, by dipping the polymer film which is the forming material ofthe polarizer (A) in a solution containing potassium. The solutiondescribed above may also be used as a solution containing iodine.

A drying method of the related art such as natural drying, blast drying,and heating drying is able to be used as a drying treatment step. Forexample, in the heating drying, a heating temperature is approximately20° C. to 80° C., and a drying time is approximately 1 minute to 10minutes. In addition, in this drying treatment step, the stretching isable to be suitably performed.

The thickness of the polarizer (A) is not particularly limited, and isgenerally 5 μm to 300 μm, is preferably 5 μm to 100 μm, and is morepreferably 5 μm to 50 μtm.

As optical properties of the polarizer (A), single transmittance at thetime of being measured in a single polarizer (A) is preferably greaterthan or equal to 43%, and is more preferably in a range of 43.3% to45.0%. In addition, it is preferable that orthogonal transmittancemeasured by preparing two polarizers (A) and by superimposing the twopolarizers (A) such that absorption axes of the two polarizers (A)mutually form 90° is smaller, in practical use, the orthogonaltransmittance is preferably greater than or equal to 0.00% and less thanor equal to 0.050%, and is more preferably less than or equal to 0.030%.The polarization degree, in practical use, is preferably greater than orequal to 99.90% and less than or equal to 100%, and is particularlypreferably greater than or equal to 99.93% and less than or equal to100%. A polarizer in which approximately the same optical properties areable to be obtained even at the time of being measured as a polarizingplate is preferable.

(Polarizing Plate Protective Film)

The optical sheet member of the present invention may or may not includea polarizing plate protective film on a side of the polarizer oppositeto the liquid crystal cell. When the optical sheet member does notinclude the polarizing plate protective film on the side of thepolarizer opposite to the liquid crystal cell, an optical conversionmaterial described below may be directly disposed on the polarizer ormay be disposed on the polymer through an adhesive agent.

Among the protective films described above, a thermoplastic resin havingexcellent transparency, mechanical strength, heat stability, moistureblocking properties, isotropy, and the like is used as the protectivefilm arranged on the side opposite to the liquid crystal cell. Specificexamples of such a thermoplastic resin include a cellulose resin such astriacetyl cellulose, a polyester resin, a polyether sulfone resin, apolysulfone resin, a polycarbonate resin, a polyamide resin, a polyimideresin, a polyolefin resin, a (meth)acrylic resin, a cyclic polyolefinresin (a norbornene-based resin), a polyarylate resin, a polystyreneresin, a polyvinyl alcohol resin, and a mixture thereof.

The cellulose resin is an ester of cellulose and a fatty acid. Specificexamples of such a cellulose ester-based resin include triacetylcellulose, diacetyl cellulose, tripropyl cellulose, dipropyl cellulose,and the like. Among them, the triacetyl cellulose is particularlypreferable. Various products of the triacetyl cellulose have beencommercially available, and the triacetyl cellulose is advantageous froma viewpoint of easiness in acquisition and cost. Examples of acommercially available product of the triacetyl cellulose includeproduct names of “UV-50”, “UV-80”, “SH-80”, “TD-80U”, “TD-TAC”, and“UZ-TAC” manufactured by Fujifilm Corporation, and a product name of “KCSeries” manufactured by Konica Minolta, Inc., and the like.

A norbornene-based resin is preferable as a specific example of thecyclic polyolefin resin. The cyclic olefin-based resin is a general termof resins in which cyclic olefin is polymerized as a polymerizationunit, and examples of the cyclic olefin-based resin include resinsdisclosed in JP1989-240517A (JP-H01-240517A), JP1991-14882A(JP-H03-14882A), JP1991-122137A (JP-H03-122137A), and the like. Specificexamples of the cyclic olefin-based resin include a ring-opening(co)polymer of cyclic olefin, an addition polymer of cyclic olefin,α-olefin and a copolymer thereof such as cyclic olefin and ethylene,propylene, or the like (representatively, a random copolymer), a graftpolymer in which these materials are modified with an unsaturatedcarboxylic acid or a derivative thereof, a hydride thereof, and thelike. Specific examples of the cyclic olefin include a norbornene-basedmonomer.

Various products have been commercially available as the cyclicpolyolefin resin. Specific examples of the cyclic polyolefin resininclude product names of “Zeonex” and “Zeonor” manufactured by ZeonCorporation, a product name of “Arton” manufactured by manufactured byJSR Corporation, a product name of “Topas” manufactured by CelaneseCorporation, and a product name of “APEL” manufactured by MitsuiChemicals, Inc.

An arbitrarily suitable (meth)acrylic resin is able to be adopted as the(meth)acrylic resin, within a range not impairing the effect of thepresent invention. Examples of the (meth)acrylic resin includepoly(meth)acrylic ester such as polymethyl methacrylate, a methylmethacrylate-(meth)acrylic acid copolymer, a methylmethacrylate-(meth)acrylic ester copolymer, a methylmethacrylate-acrylic ester-(meth)acrylic acid copolymer, a methyl(meth)acrylate-styrene copolymer (an MS resin or the like), and apolymer having an alicyclic hydrocarbon group (for example, methylmethacrylate-cyclohexyl methacrylic acid copolymer, a methylmethacrylate-norbornyl (meth)acrylic acid copolymer, and the like).Preferably, examples of the (meth)acrylic resin include an C1-6polyalkyl (meth)acrylate such as polymethyl (meth)acrylate. Morepreferably, examples of the (meth)acrylic resin include a methylmethacrylate-based resin in which methyl methacrylate is a maincomponent (50 mass % to 100 mass %, and preferably 70 mass % to 100 mass%).

Specific examples of the (meth)acrylic resin include Acrypet VH andAcrypet VRL20A manufactured by Mitsubishi Rayon Co., Ltd., a(meth)acrylic resin having a ring structure in the molecule which isdisclosed in JP2004-70296A, and a (meth)acrylic resin having high Tgobtained by a cross-linkage in the molecule or a cyclization reaction inthe molecule.

A (meth)acrylic resin having a lactone ring structure is able to be usedas the (meth)acrylic resin. This is because the (meth)acrylic resin hashigh heat resistance, high transparency, and high mechanical strengthdue to biaxial stretching.

The thickness of the protective film is able to be suitably set, and isgenerally approximately 1 μm to 200 μm from a viewpoint of workabilitysuch as strength or handling, thin layer properties, and the like. Inparticular, the thickness of the protective film is preferably 1 μm to100 μm, and is more preferably 5 μm to 80 μm. It is particularlypreferable that the thickness of the protective film is 5 μm to 40 μm.

Re(λ) and Rth(λ) respectively indicate in-plane retardation andretardation in a thickness direction at a wavelength of λ. Re(λ) ismeasured by allowing light having a wavelength of λ nm to be incident ina film normal direction using KOBRA 21ADH or WR (manufactured by OjiScientific Instruments). In selection of a measurement wavelength of λnm, a wavelength selective filter is manually exchanged or a measurementvalue is converted by using a program or the like, and thus themeasurement is able to be performed. When a film to be measured isdenoted by monoaxial or biaxial refractive index ellipsoid, Rth(λ) iscalculated by the following method. Furthermore, a part of thismeasurement method is used in measurement of an average tilt angle of adiscotic liquid crystal molecule on an alignment film side in an opticalanisotropic layer described below and an average tilt angle on a sideopposite to the alignment film side.

In Rth(λ), Re(λ) described above is measured at total 6 points byallowing light having a wavelength of λ nm to be incident fromdirections respectively inclined in 10° step from a normal direction to50° on one side with respect to a film normal direction in which anin-plane slow axis (determined by KOBRA 21ADH or WR) is used as aninclination axis (a rotational axis) (when there is no slow axis, anarbitrary direction of a film plane is used as the rotational axis), andKOBRA 21ADH or WR is calculated on the basis of the measured retardationvalue, an assumed value of the average refractive index, and the inputfilm thickness value. In the above description, in a case of a filmhaving a direction in which a retardation value at a certain inclinationangle is zero by using the in-plane slow axis as the rotational axisfrom the normal direction, a retardation value at an inclination anglegreater than the inclination angle described above is changed to have anegative sign, and then KOBRA 21ADH or WR is calculated. Furthermore, aretardation value is measured from two arbitrarily inclined directionsby using the slow axis as the inclination axis (the rotational axis)(when there is no slow axis, an arbitrary direction of the film plane isused as the rotational axis), and Rth is able to be calculated byExpression (A) and Expression (B) described below on the basis of theretardation value, an assumed value of the average refractive index, andthe input film thickness value.

$\begin{matrix}{{{Re}(\theta)} = {\left\lbrack {{nx} - \frac{{ny} \times {nz}}{\sqrt{\begin{matrix}{\left( {{ny}\; {\sin \left( {\sin^{- 1}\left( \frac{\sin \left( {- \theta} \right)}{nx} \right)} \right)}} \right)^{2} +} \\\left( {{nz}\; {\cos \left( {\sin^{- 1}\left( \frac{\sin \left( {- \theta} \right)}{nx} \right)} \right)}} \right)^{2}\end{matrix}}}} \right\rbrack \times \frac{d}{\cos \left( {\sin^{- 1}\left( \frac{\sin \left( {- \theta} \right)}{nx} \right)} \right)}}} & {{Expression}\mspace{14mu} (A)}\end{matrix}$

Furthermore, Re(θ) described above indicates a retardation value in adirection inclined by an angle of θ from the normal direction. Inaddition, in Expression (A), nx represents a refractive index in theslow axis direction in the plane, ny represents a refractive index in adirection orthogonal to nx in the plane, and nz represents a refractiveindex in a direction orthogonal to nx and ny. d is a film thickness.

Rth=((nx+ny)/2−nz)×d  Expression (B)

When the measured film is a so-called film not having an optic axiswhich is not able to be denoted by a monoaxial or biaxial refractiveindex ellipsoid, Rth(λ) is calculated by the following method. InRth(λ), Re(λ) described above is measured at 11 points by allowing lighthaving a wavelength of λ nm to be incident from directions respectivelyinclined in 10° step from −50° to +50° with respect to the film normaldirection in which the in-plane slow axis (determined by KOBRA 21ADH orWR) is used as the inclination axis (the rotational axis), and KOBRA21ADH or WR is calculated on the basis of the measured retardationvalue, an assumed value of the average refractive index, and the inputfilm thickness value. In addition, in the measurement described above, acatalog value of various optical films in a polymer handbook (JOHNWILEY&SONS, INC) is able to be used as the assumed value of the averagerefractive index. When the value of the average refractive index is notknown in advance, the value of the average refractive index is able tobe measured by using an Abbe's refractometer. The value of the averagerefractive index of a main optical film will be exemplified as follows:cellulose acylate (1.48), a cycloolefin polymer (1.52), polycarbonate(1.59), polymethyl methacrylate (1.49), and polystyrene (1.59). Theassumed values of the average refractive index and the film thicknessare input, and thus nx, ny, and nz are calculated by KOBRA 21ADH or WR.Nz=(nx−nz)/(nx−ny) is further calculated by the calculated nx, ny, andnz.

Furthermore, herein, “visible light” indicates light at 380 nm to 780nm. In addition, herein, the measurement wavelength is 550 nm unlessotherwise specified.

In addition, herein, angles (for example, angles such as “90°”) and arelationship thereof (for example, “orthogonal”, “parallel”, and“intersecting at 45°”, and the like) are in a range of an error which isallowable in a technical field of the present invention. For example,the angle indicates that the angle is in a range of less than ±10° froman exact angle, and an error from the exact angle is preferably lessthan or equal to 5°, and is more preferably less than or equal to 3°.

Herein, the “slow axis” of the retardation film or the like indicates adirection in which the refractive index is maximized.

In addition, herein, a numerical value, a numerical range, andquantitative expression (for example, the expression such as “equal” and“identical”) indicating optical properties of each member such as aphase difference region, a retardation film, and a liquid crystal layerare interpreted as a numerical value, a numerical range, and propertiesincluding an error which is generally allowable in a liquid crystaldisplay device or members used therein.

In addition, herein, a “front surface” indicates the normal directionwith respect to a display surface, and “front contrast (CR)” indicatescontrast calculated from white brightness and black brightness which aremeasured in the normal direction of the display surface, and “view anglecontrast (CR)” indicates contrast calculated from white brightness andblack brightness which are measured in a direction inclined from thenormal direction of the display surface (for example, a directiondefined by 60° in a polar angle direction with respect to the displaysurface).

(Adhesive Layer)

In order to bond the polarizer (A) to the protective film, an adhesiveagent, an adhesive agent, and the like are able to be suitably adoptedaccording to the polarizer (A) and the protective film. This adhesiveagent and an adhesion treatment method are not particularly limited, andfor example, the adhesion treatment method is able to be performedthrough an adhesive agent formed of a vinyl polymer, an adhesive agentformed of a water-soluble cross-linking agent of a vinyl alcohol-basedpolymer such as at least a boric acid or borax, glutaraldehyde ormelamine, and an oxalic acid. The adhesive layer formed of such anadhesive agent is able to be formed as a coated and dried layer of anaqueous solution, and when this aqueous solution is prepared, asnecessary, a cross-linking agent or other additives, and a catalyst suchas an acid are able to be mixed. In particular, when a polyvinylalcohol-based polymer film is used as the polarizer (A), it ispreferable that an adhesive agent containing a polyvinyl alcohol-basedresin is used from a viewpoint of adhesiveness. Further, it is morepreferable that an adhesive agent containing a polyvinyl alcohol-basedresin having an acetoacetyl group is used from a viewpoint of improvingdurability.

The polyvinyl alcohol-based resin described above is not particularlylimited, and the average degree of polymerization is approximately 100to 3,000, and the average degree of saponification is preferably 85 mol% to 100 mol %, from a viewpoint of adhesiveness. In addition, theconcentration of the adhesive agent aqueous solution is not particularlylimited, and the concentration of the adhesive agent aqueous solution ispreferably 0.1 mass % to 15 mass %, and is more preferably 0.5 mass % to10 mass %. The thickness of the adhesive layer described above ispreferably approximately 30 nm to 1,000 nm, and is more preferably 50 nmto 300 nm, in the thickness after drying. When the thickness isexcessively thin, an adhesion force becomes insufficient, and when thethickness is excessively thick, a problem is more likely to occur in theappearance.

An ultraviolet curable resin or a thermosetting resin such as a(meth)acrylic resin, an urethane-based resin, an acryl urethane-basedresin, an epoxy-based resin, and a silicone-based resin is able to beused as the other adhesive agent.

<Brightness Enhancement Film>

In the first aspect of the optical sheet member of the presentinvention, the brightness enhancement film described above has areflection center wavelength in a wavelength range of 400 nm to 500 nm(preferably in a wavelength range of 430 nm to 480 nm) and a peak ofreflectivity having a half-value width of less than or equal to 100 nm.

In the second aspect of the optical sheet member of the presentinvention, the brightness enhancement film described above has areflection center wavelength in a wavelength range of 300 nm to 430 nmand a peak of reflectivity having a half-value width of less than orequal to 100 nm.

According to the brightness enhancement film having such aconfiguration, light in a first polarization state is able to besubstantially reflected by a reflection polarizer, and light in a secondpolarization state is able to be substantially transmitted through thereflection polarizer described above, and the light in the firstpolarization state which is substantially reflected by the reflectionpolarizer is recirculated in a random direction and a randompolarization state by a reflection member described below (such as alight guide device and an optical resonator), and thus brightness of animage display device is able to be improved.

In the optical sheet member of the present invention, the film thicknessof the brightness enhancement film itself is preferably 1 μm to 30 μm,is more preferably 1 μm to 10 μm, and is particularly preferably 1 μm to9μm, from a viewpoint of a demand for thinning recent portable devices.

The following aspect (i) or (ii) is preferable as the brightnessenhancement film described above in each of the first aspect of theoptical sheet member of the present invention and the second aspect ofthe optical sheet member of the present invention.

-   -   Aspect (i) of the first aspect of the optical sheet member of        the present invention: It is preferable that the reflection        polarizer (B) includes the light reflecting layer which has a        reflection center wavelength in a wavelength range of 400 nm to        500 nm (preferably, in a wavelength range of 430 nm to 480 nm)        and a peak of reflectivity having a half-value width of less        than or equal to 100 nm, and is formed by fixing a cholesteric        liquid crystalline phase, and the brightness enhancement film        includes the λ/4 plate (C) between the optical conversion        member (D) and the reflection polarizer (B) in which at least        one of Expressions (1) and (2) described below is satisfied.        Further, the wavelength dispersion of the λ/4 plate (C) may be a        forward dispersion “Re(450)>Re(550)”, and as the wavelength        dispersion of the λ/4 plate (C), a flat dispersion        “Re(450)≅Re(550)” is able to be preferably used, and a reverse        dispersion “Re(450)<Re(550)” is able to be more preferably used.

450 nm/4−60 nm<Re(450)<450 nm/4 +60 nm  Expression (1)

(In Expression (1), Re(λ) represents retardation in an in-planedirection at a wavelength of λ nm (unit: nm).)

-   -   Aspect (ii) of the first aspect of the optical sheet member of        the present invention:        The reflection polarizer (B) is the dielectric multilayer film        which has a reflection center wavelength in a wavelength range        of 400 nm to 500 nm (preferably, in a wavelength range of 430 nm        to 480 nm) and a peak of reflectivity having a half-value width        of less than or equal to 100 nm.    -   Aspect (i) of the second aspect of the optical sheet member of        the present invention:        It is preferable that the reflection polarizer (B) includes the        light reflecting layer which has a reflection center wavelength        in a wavelength range of 300 nm to 430 nm and a peak of        reflectivity having a half-value width of less than or equal to        100 nm, and is formed by fixing a cholesteric liquid crystalline        phase, and the brightness enhancement film includes the λ/4        plate (C) between the optical conversion member (D) and the        reflection polarizer (B) in which Expression (2) described below        is satisfied. Further, the wavelength dispersion of the λ/4        plate (C) may be a forward dispersion “Re(380)>Re(450)”, and as        the wavelength dispersion of the λ/4 plate (C), a flat        dispersion “Re(380)≅Re(450)” is able to be preferably used, and        a reverse dispersion “Re(380)<Re(450)” is able to be more        preferably used.

380 nm/4−60 nm<Re(380)<380 nm/4+60 nm  Expression (2)

(In Expression (2), Re(λ) represents retardation in an in-planedirection at a wavelength of λ nm (unit: nm).)

-   -   Aspect (ii) of the second aspect of the optical sheet member of        the present invention:        It is preferable that the reflection polarizer (B) is the        dielectric multilayer film which has a reflection center        wavelength in a wavelength range of 300 nm to 430 nm and a peak        of reflectivity having a half-value width of less than or equal        to 100 nm.

In FIG. 1 to FIG. 10, specific examples of the aspect (i) areillustrated in FIG. 1 to FIG. 5, and specific examples of the aspect(ii) are illustrated in FIG. 6 to FIG. 10.

First, the aspect (i) will be described.

The light reflecting layer formed by fixing a cholesteric liquidcrystalline phase is able to reflect at least one of right circularpolarization light and left circular polarization light in a wavelengthrange in the vicinity of the reflection center wavelength thereof. Inaddition, the λ/4 plate is able to convert light having a wavelength ofλ nm into linear polarization light from circular polarization light.According to the brightness enhancement film having a configuration suchas the aspect (i), light in the first polarization state (for example,the right circular polarization light) is substantially reflected by thereflection polarizer, whereas light in the second polarization state(for example, the left circular polarization light) is substantiallytransmitted through the reflection polarizer described above, and thelight in the second polarization state (for example, the left circularpolarization light) which is transmitted through the reflectionpolarizer described above is converted into the linear polarizationlight by the λ/4 plate (C) in which Expression (1) is satisfied or theλ/4 plate (C) in which Expression (2) is satisfied and is able to besubstantially transmitted through the polarizer (a linear polarizer) ofthe polarizing plate described above.

In the aspect (i), it is preferable that the reflection polarizer (B)described above includes only one light reflecting layer formed byfixing a cholesteric liquid crystalline phase, that is, it is preferablethat the reflection polarizer (B) described above does not include otherlayers formed by fixing a cholesteric liquid crystalline phase, from aviewpoint of thinning the film thickness of the brightness enhancementfilm described above.

In FIG. 1 to FIG. 4, aspects are illustrated in which a light reflectinglayer 14B formed by fixing a cholesteric liquid crystalline phase islaminated on a λ/4 plate 12 in which Expression (1) is satisfied throughthe adhesive layer 20. In FIG. 5, an aspect is illustrated in which alight reflecting layer 14UV formed by fixing a cholesteric liquidcrystalline phase is laminated on the λ/4 plate 12 in which Expression(2) is satisfied through the adhesive layer 20. However, the presentinvention is not limited by such specific examples, the light reflectinglayer 14B may be in direct contact with the λ/4 plate 12 in whichExpression (1) is satisfied, and the light reflecting layer 14UV may bein direct contact with the λ/4 plate 12 in which Expression (2) issatisfied. In addition, the λ/4 plate 12 in which Expression (1) issatisfied and the λ/4 plate 12 in which Expression (2) is satisfied maybe a single layer or may be a laminated body of two or more layers, andit is more preferable that the λ/4 plate 12 is the laminated body of twoor more layers from a viewpoint of controlling the wavelength dispersionof birefringence.

The direction of the linear polarization light which is transmittedthrough the λ/4 plate used in the present invention is laminated to beparallel to a transmission axis direction of the backlight sidepolarizing plate.

When the λ/4 plate is the single layer, an angle between the slow axisdirection of the λ/4 plate and the absorption axis direction of thepolarizing plate is 30° to 60°, is preferably 35° to 55°, is morepreferably 40° to 50°, and is particularly preferably 45°.

In addition, the spiral structure of the cholesteric liquid crystallinephase and the polarization state of the light are variously defined, andin the present invention, when the light is sequentially transmittedthrough the light reflecting layer formed by fixing a cholesteric liquidcrystalline phase, the λ/4 plate layer, and the polarizing plate layer,an arrangement is preferable in which brightness is maximized

Accordingly, when the direction of the spiral structure of the lightreflecting layer formed by fixing a cholesteric liquid crystalline phaseis a right spiral (the light reflecting layer formed by fixing acholesteric liquid crystalline phase in which a right chiral materialdescribed in an example herein is used), it is necessary that lightexited from the light reflecting layer formed by fixing a cholestericliquid crystalline phase is coincident with a transmission axis of thebacklight side polarizing plate. For this reason, when the direction ofthe spiral structure of the light reflecting layer formed by fixing acholesteric liquid crystalline phase is a right spiral in the exampleherein, as illustrated in FIG. 12, it is necessary that a slow axisdirection 12 s 1 of the λ/4 plate has the angle described above in aclockwise direction from an absorption axis direction 3 ab of thepolarizer when seen from the backlight side. On the other hand, when thedirection of the spiral structure of the light reflecting layer formedby fixing a cholesteric liquid crystalline phase is a left spiral, asillustrated in FIG. 13, it is necessary that the slow axis direction 12s 1 of the λ/4 plate has the angle described above in the clockwisedirection from the absorption axis direction 3 ab of the polarizer whenseen from the backlight side.

The light reflecting layer 14B has a reflection center wavelength in awavelength range of 430 nm to 480 nm and a peak of reflectivity having ahalf-value width of less than or equal to 100 nm.

It is preferable that the reflection center wavelength of the lightreflecting layer 14B is in a wavelength range of 430 nm to 470 nm.

The half-value width of the peak of the reflectivity of the lightreflecting layer 14B is preferably less than or equal to 100 nm, is morepreferably less than or equal to 80 nm, and is particularly preferablyless than or equal to 70 nm.

The light reflecting layer 14UV has a reflection center wavelength in awavelength range of 300 nm to 430 nm and a peak of reflectivity having ahalf-value width of less than or equal to 100 nm.

It is preferable that the reflection center wavelength of the lightreflecting layer 14UV is in a wavelength range of 300 nm to 380 nm.

The half-value width of the peak of the reflectivity of the lightreflecting layer 14UV is preferably less than or equal to 100 nm, ismore preferably less than or equal to 80 nm, and is particularlypreferably less than or equal to 70 nm.

The wavelength applying a peak is able to be adjusted by changing thepitch or the refractive index of the cholesteric liquid crystal layer,and the pitch is able to be easily adjusted by changing an added amountof a chiral agent. Specifically, the details are described in Fuji FilmResearch & Development No.50 (2005) pp.60-63.

The chiral agent described above is able to be selected from variousknown chiral agents (for example, disclosed in Liquid Crystal DeviceHandbook, Chapter 3, Section 4-3, Chiral Agent for TN and STN, Page 199,Japan Society for the Promotion of Science, Edited by First 42Committee, 1989). In general, the chiral agent contains an asymmetriccarbon atom, but an axial asymmetric compound or a planar asymmetriccompound which does not contain an asymmetric carbon atom is also ableto be used as the chiral agent. In an example of the axial asymmetriccompound or a planar asymmetric compound, binaphthyl, helicene,paracyclophane, and a derivative thereof are included. The chiral agentmay have a polymerizable group. When the chiral agent has apolymerizable group and a rod-like liquid crystal compound which is usedtogether also has a polymerizable group, it is possible to form apolymer having a repeating unit derived from the rod-like liquid crystalcompound and a repeating unit derived from the chiral agent by apolymerization reaction between the chiral agent having a polymerizablegroup and the polymerizable rod-like liquid crystal compound. In thisaspect, it is preferable that the polymerizable group of the chiralagent having a polymerizable group is the same polymerizable group asthat of the polymerizable rod-like liquid crystal compound. Accordingly,the polymerizable group of the chiral agent is preferably an unsaturatedpolymerizable group, an epoxy group, or an aziridinyl group, is morepreferably the unsaturated polymerizable group, and is particularlypreferably an ethylenically unsaturated polymerizable group.

In addition, the chiral agent described above may be a liquid crystalcompound.

Examples of the chiral agent exhibiting strong twisting force includechiral agents disclosed in JP2010-181852A, JP2003-287623A,JP2002-80851A, JP2002-80478A, and JP2002-302487A, and are able to bepreferably used in the present invention. Further, as isosorbidecompounds disclosed in these publications, isomannide compounds having acorresponding structure are able to be used, and as isomannide compoundsdisclosed in these publications, isosorbide compounds having acorresponding structure are able to be used.

A manufacturing method of the light reflecting layer formed by fixingthe cholesteric liquid crystalline phase which is used in the aspect (i)is not particularly limited, and for example, methods disclosed inJP1989-133003A (JP-H01-133003A), JP3416302B, JP3363565B, andJP1996-271731A (JP-H08-271731A) are able to be used as the manufacturingmethod of the light reflecting layer, and the contents of thesepublications are incorporated in the present invention.

Hereinafter, a method disclosed in JP1996-271731A (JP-H08-271731A) willbe described.

When the cholesteric liquid crystal layer described above issuperimposed, it is preferable that a combination in which the circularpolarization light in the same direction is reflected is used.Accordingly, it is possible to prevent a phase state of the circularpolarization light which is reflected on each layer from being alignedin a different polarization state in each wavelength region, and thus itis possible to increase utilization efficiency of light.

The cholesteric liquid crystal is a layer formed by fixing this liquidcrystal compound due to polymerization or the like, and it is notnecessary that the cholesteric liquid crystal exhibits liquidcrystalline properties after the layer is formed. The polymerizableliquid crystal compound may be a multifunctional polymerizable liquidcrystal or a monofunctional polymerizable liquid crystal compound. Inaddition, the liquid crystal compound may be a discotic liquid crystalcompound described below or a rod-like liquid crystal compound.

Rod-Like Liquid Crystal Compound

Azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic esters,phenyl cyclohexane carboxylic esters, cyanophenyl cyclohexanes,cyano-substituted phenyl pyrimidines, alkoxy-substituted phenylpyrimidines, phenyl dioxanes, trans, and alkenyl cyclohexylbenzonitriles are preferably used as the rod-like liquid crystalcompound. Not only low molecular weight liquid crystal molecules asdescribed above but also high molecular weight liquid crystal moleculesare able to be used as the rod-like liquid crystal compound.

It is preferable that alignment is fixed by polymerizing the rod-likeliquid crystal compound, and compounds disclosed in Makromol. Chem.,Vol. 190, Page 2255 (1989), Advanced Materials, Vol. 5, Page 107 (1993),U.S. Pat. No. 4,683,327A, U.S. Pat. No. 5,622,648A, U.S. Pat. No.5,770,107A, WO95/22586A, WO95/24455A, WO97/00600A, WO98/23580A,WO98/52905A, JP1989-272551A (JP-H01-272551A), JP1994-16616A(JP-H06-16616A), JP1995-110469A (JP-H07-110469A), JP1999-80081A(JP-H11-80081A), JP2001-64627, and the like are able to be used as thepolymerizable rod-like liquid crystal compound. Further, for example,compounds disclosed in JP1999-513019A (JP-H11-513019A) or JP2007-279688Aare also able to be preferably used as the rod-like liquid crystalcompound.

Disk-Like Liquid Crystal Compound

Hereinafter, the light reflecting layer formed by fixing a cholestericliquid crystalline phase in which a disk-like liquid crystal compound isused as a cholesteric liquid crystal material will be described.

For example, compounds disclosed in JP2007-108732A or JP2010-244038A areable to be preferably used as the disk-like liquid crystal compound, butthe present invention is not limited thereto.

Hereinafter, preferred examples of the disk-like liquid crystal compoundwill be described, but the present invention is not limited thereto.

Other Component

The compositions used for forming the light reflecting layer formed byfixing a cholesteric liquid crystalline phase may contain othercomponents such as a chiral agent, an alignment control agent, apolymerization initiator, and an alignment aid in addition to thecholesteric liquid crystal material.

Examples of the alignment control agent described above include acompound exemplified in “0092” and “0093” of JP2005-99248A, a compoundexemplified in “0076” to “0078” and “0082” to “0085” of JP2002-129162A,a compound exemplified in “0094” and “0095” of JP2005-99248A, and acompound exemplified “0096” of JP2005-99248A.

A compound denoted by General Formula (I) described below is preferableas the fluorine-based alignment control agent.

(Hb¹¹—Sp¹¹—L¹¹—Sp¹²—L¹²)_(m11)—A¹¹—L¹³—T¹¹—L¹⁴—A¹²—(L¹⁶—Sp¹³—L¹⁶—Sp¹⁴—Hb¹¹)_(n11)  GeneralFormula (I)

In General Formula (I), L¹¹, L¹², L¹³, L¹⁴, L¹⁵, and L¹⁶ eachindependently represent a single bond, —O—, —S—, —CO—, —COO—, —OCO—,—COS—, —SCO—, —NRCO—, and —CONR— (in General Formula (I), R represents ahydrogen atom or an alkyl group having 1 to 6 carbon atoms), —NRCO— and—CONR— has an effect of reducing solubility, —O—, —S—, —CO—, —COO—,—OCO—, —COS—, and —SCO— are more preferable from a viewpoint of thetendency of increasing a haze value at the time of forming a film, and—O—, —CO—, —COO—, and —OCO— are even more preferable from a viewpoint ofstability of the compound. The alkyl group which is able to be includedin R may be straight chained alkyl group or a branched alkyl group. Thenumber of carbon atoms is preferably 1 to 3, and a methyl group, anethyl group, and an n-propyl group are able to be exemplified as thealkyl group.

Examples of the photopolymerization initiator include an a-carbonylcompound (disclosed in each of the specification of U.S. Pat. No.2,367,661A and U.S. Pat. No. 2,367,670A), acyloin ether (disclosed inthe specification of U.S. Pat. No. 2,448,828A), an a-hydrocarbonsubstituted aromatic acyloin compound (disclosed in the specification ofU.S. Pat. No. 2,722,512A), a polynuclear quinone compound (disclosed inthe specification of U.S. Pat. No. 3,046,127A and U.S. Pat. No.2,951,758A), a combination of a triaryl imidazole dimer andp-aminophenyl ketone (disclosed in the specification of U.S. Pat. No.3,549,367A), an acridine compound and a phenazine compound (disclosed inthe publication of JP1985-105667A (JP-S60-105667A) and in thespecification of U.S. Pat. No. 4239850A), an oxadiazole compound(disclosed in the specification of U.S. Pat. No. 4212970A), and an acylphosphine oxide compound (disclosed in the publication of JP1988-40799B(JP-S63-40799B), JP1993-29234B (JP-H05-29234B), JP1998-95788A(JP-H10-95788A), and JP1998-29997A (JP-H10-29997A), and the like.

Solvent:

An organic solvent is preferably used as a solvent of the compositionfor forming each of the light reflecting layers. Examples of the organicsolvent include amide (for example, N,N-dimethyl formamide), sulfoxide(for example, dimethyl sulfoxide), a heterocyclic compound (for example,pyridine), hydrocarbon (for example, benzene and hexane), alkyl halide(for example, chloroform and dichloromethane), ester (for example,methyl acetate and butyl acetate), ketone (for example, acetone, methylethyl ketone, and cyclohexanone), and ether (for example,tetrahydrofuran, and 1,2-dimethox ethane). Among them, the alkyl halideand the ketone are preferable. Two or more types of the organic solventsmay be used together.

In addition, a suitable cholesteric liquid crystal may be used as thecholesteric liquid crystal, but is not particularly limited, and aliquid crystal polymer is also able to be used as the cholesteric liquidcrystal. In addition, it is preferable that the wavelength region ofselective reflection is widened as the birefringence of the cholestericliquid crystal molecule becomes larger.

In this viewpoint, a high An liquid crystal material disclosed inparagraphs of “0153” to “0171” of JP2011-510915A is able to be used.

A suitable liquid crystal polymer, for example, a main chain type liquidcrystal polymer such as polyester, a side chain type liquid crystalpolymer formed of an acrylic main chain or a methacrylic main chain, asiloxane main chain, and the like, a nematic liquid crystal polymercontaining a low molecular chiral agent, a liquid crystal polymerintroduced with a chiral component, a nematic-based andcholesteric-based mixed liquid crystal polymer, and the like are used asthe liquid crystal polymer described above. It is preferable that aglass transition temperature is 30° C. to 150° C. from a viewpoint ofhandleability.

The cholesteric liquid crystal layer is able to be formed by using asuitable method such as a method of directly coating a polarizationseparating plate through a suitable alignment film such as an obliquevapor deposition layer of polyimide or polyvinyl alcohol, and SiO, asnecessary, a method of coating a support body which does not deteriorateat an alignment temperature of a liquid crystal polymer formed of atransparent film or the like through an alignment film, as necessary. Asupport body having a phase difference as small as possible ispreferably used as the support body from a viewpoint of preventing achange in a polarization state. In addition, a superimposition method ofthe cholesteric liquid crystal layer through the alignment film, and thelike are able to be adopted.

Furthermore, the liquid crystal polymer is able to be coated with aliquid material such as a solution of a solvent or a melting liquid dueto heating by using a suitable method such as a roll coating method or agravure printing method, and a spin coating method.

The polymerization reaction includes a thermal polymerization reactionusing a thermal polymerization initiator and a photopolymerizationreaction using a photopolymerization initiator. Among them, thephotopolymerization reaction is preferable. It is preferable that anultraviolet ray is used in light irradiation for polymerizing the liquidcrystal molecule. Irradiation energy is preferably 20 mJ/cm² to 50J/cm²,and is more preferably 100 mJ/cm² to 800 mJ/cm². In order to acceleratethe photopolymerization reaction, the light irradiation may be performedin heating conditions. The thickness of the light reflecting layerformed by fixing a cholesteric liquid crystalline phase to be formed ispreferably 0.1 μm to 100 μm, is more preferably 0.5 μm to 50 μm, is evenmore preferably 1 μm to 30 μm, and is most preferably 2 μm to 20 μm,from a viewpoint of preventing selective reflectivity, alignmentdisorder, and a decrease in transmittance.

When each of the light reflecting layers of the brightness enhancementfilm of the present invention is formed by coating, it is preferablethat each of the light reflecting layers is formed by drying andsolidifying a coating liquid by using a known method after the coatingwith the coating liquid described above. Drying by heating is preferableas a drying method.

In the aspect (i) of the first aspect of the optical sheet member of thepresent invention, the brightness enhancement film includes the λ/4plate (C) between the optical conversion member (D) and the reflectionpolarizer (B) in which Expression (1) described below is satisfied.Further, the wavelength dispersion of the λ/4 plate (C) may be a forwarddispersion “Re(450)>Re(550)”, and as the wavelength dispersion of theλ/4 plate (C), a flat dispersion “Re(450)≅Re(550)” is able to bepreferably used, and a reverse dispersion “Re(450)<Re(550)” is able tobe more preferably used.

450 nm/4−60 nm <Re(450)<450 nm/4+60 nm  Expression (1)

(In Expression (1), Re(λ) represents retardation (unit: nm) in anin-plane direction at a wavelength of λ nm.)

It is more preferable that Expression (1′) described below is satisfiedin the λ/4 plate (C) in which Expression (1) described above issatisfied.

450 nm/4−25 nm<Re(450)<450 nm/4+25 nm  Expression (1′)

It is particularly preferable that Expression (1″) described below issatisfied in the λ/4 plate (C) in which Expression (1) described aboveis satisfied.

450 nm/4−15 nm<Re(450)<450 nm/4+15 nm  Expression (1″)

In the aspect (i) of the second aspect of the optical sheet member ofthe present invention, the brightness enhancement film includes the λ/4plate (C) between the optical conversion member (D) and the reflectionpolarizer (B) in which Expression (2) described below is satisfied.Further, the wavelength dispersion of the λ/4 plate (C) may be a forwarddispersion “Re(380)>Re(450)”, and as the wavelength dispersion of theλ/4 plate (C), a flat dispersion “Re(380)≅Re(450)” is able to bepreferably used, and a reverse dispersion “Re(380)<Re(450)” is able tobe more preferably used.

380 nm/4−60 nm<Re(380)<380 nm/4+60 nm  Expression (2)

(In Expression (2), Re(λ) represents retardation (unit: nm) in anin-plane direction at a wavelength of λ nm.)

It is more preferable that Expression (2′) described below is satisfiedin the λ/4 plate (C) in which Expression (2) described above issatisfied.

380 nm/4−25 nm<Re(380)<380 nm/4+25 nm  Expression (2′)

It is particularly preferable that Expression (2″) described below issatisfied in the λ/4 plate (C) in which Expression (2) described aboveis satisfied.

380 nm/4-15 nm <Re(380)<380 nm/4+15 nm  Expression (2″)

A manufacturing method of the λ/4 plate (C) in which Expression (1) issatisfied and the λ/4 plate in which Expression (2) is satisfied, whichare used in the aspect (i) is not particularly limited, and for example,a method disclosed in JP1996-271731A (JP-H08-271731A) is able to be usedas the manufacturing method, and the contents of this publication areincorporated in the present invention.

Hereinafter, the method disclosed in JP1996-271731A (JP-H08-271731A)will be described.

Examples of a ¼ wavelength plate formed of a superimposed body of theretardation film include a ¼ wavelength plate formed by combining aretardation film applying a phase difference of a ½ wavelength withrespect to monochromatic light and a retardation film applying a phasedifference of a ¼ wavelength with respect to monochromatic light, and bylaminating the retardation films such that optical axes of a pluralityof retardation films intersect with each other.

In such a case, the plurality of retardation films applying the phasedifference of the ½ wavelength or the ¼ wavelength with respect to themonochromatic light are laminated such that the optical axes intersectwith each other, and thus a wavelength dispersion of retardation whichis defined by the product (Δnd) of a refractive index difference (Δn)and a thickness (d) of birefringence light is able to be superimposed oradjusted, and is able to be arbitrarily controlled, the wavelengthdispersion is suppressed while controlling the entire phase differenceto the ¼ wavelength, and thus a wavelength plate indicating a phasedifference of a ¼ wavelength over a wide wavelength region is able to beobtained.

In the above description, the number of laminations of the retardationfilm is an arbitrary number. Two to five retardation films are generallylaminated from a viewpoint of transmittance of light or the like. Inaddition, the arrangement position of the retardation film applying thephase difference of the ½ wavelength and the retardation film applyingthe phase difference of the ¼ wavelength is also arbitrary.

In addition, when retardation of light having a wavelength of 450 nm isset to R₄₅₀, and retardation of light having a wavelength of 550 nm isset to R₅₅₀, a ¼ wavelength plate formed of a superposed body ofretardation films is able to be obtained by laminating a retardationfilm having large retardation at R₄₅₀/R₅₅₀ of 1.00 to 1.05 and aretardation film having small retardation at R₄₅₀/R₅₅₀ of 1.05 to 1.20such that optical axes thereof intersect with each other.

In such a case, the retardation films having different retardations arelaminated such that the optical axes intersect with each other, inparticular, are orthogonal to each other, and thus the wavelengthdispersion of the retardation of each of the retardation films is ableto be superimposed or adjusted, and is able to be controlled, and inparticular, the retardation is able to be reduced towards a shortwavelength side.

In addition, specific examples of the ¼ wavelength plate described aboveinclude a ¼ wavelength plate which is formed by laminating a retardationfilm (retardation of light having a wavelength of 550 nm:700 nm) formedby performing a stretching treatment with respect to a polyvinyl alcoholfilm and a retardation film (retardation of light having a wavelength of550 nm:560 nm) formed by performing a stretching treatment with respectto a polycarbonate film such that the optical axes thereof areorthogonal to each other. Such a lamination approximately functions asthe ¼ wavelength plate over a wavelength of 450 nm to 650 nm.

The λ/4 plate may be an optical anisotropic support body having adesired λ/4 function in the support body itself, or may include anoptical anisotropic layer or the like on a support body formed of apolymer film.

When the λ/4 plate is the optical anisotropic support body having adesired λ/4 function in the support body itself, for example, theoptical anisotropic support body is able to be obtained by a method inwhich a polymer film is monoaxially or biaxially stretched. The type ofthe polymer is not particularly limited, and a polymer having excellenttransparency is preferably used. Examples of the polymer include thematerials used in the λ/4 plate described above, a cellulose acylatefilm (for example, a cellulose triacetate film (a refractive index of1.48), a cellulose diacetate film, a cellulose acetate butyrate film,and a cellulose acetate propionate film), polyolefin such aspolyethylene and polypropylene, a polyester-based resin film such aspolyethylene terephthalate or polyethylene naphthalate, a polyacrylicresin film such as a polyether sulfone film and polymethyl methacrylate,a polyurethane-based resin film, a polyester film, a polycarbonate film,a polysulfone film, a polyether film, a polymethyl pentene film, apolyether ketone film, a (meth)acrylonitrile film, polyolefin, a polymerhaving an alicyclic structure (a norbornene-based resin (a product name:Arton, manufactured by JSR Corporation) and amorphous polyolefin (aproduct name: Zeonex, manufactured by Zeon Corporation)), and the like.Among them, the triacetyl cellulose, the polyethylene terephthalate, andthe polymer having an alicyclic structure are preferable, and thetriacetyl cellulose is particularly preferable.

As described below, the angle between the slow axis direction of the λ/4plate and the absorption axis direction of the polarizing plate is 30°to 60°, is preferably 35° to 55°, is more preferably 40° to 50°, and isparticularly preferably 45°. When the polarizing plate is formed byusing a roll-to-roll process, in general, a longitudinal direction (atransportation direction) is the absorption axis direction, and thus itis preferable that the angle between the slow axis direction and thelongitudinal direction of the λ/4 plate is 30° to 60°. A manufacturingmethod of the λ/4 plate in which the angle between the slow axisdirection and the longitudinal direction is 30° to 60° is notparticularly limited insofar as an alignment axis of the polymer isinclined by a desired angle by continuously stretching the polymer in adirection at 30° to 60° with respect to the longitudinal direction, anda known method is able to be adopted as the manufacturing method. Inaddition, a stretching machine used in inclined stretching is notparticularly limited, and a known tenter stretching machine of therelated art in which feeding force, tensile force, or pulling force isable to be added at different left and right rates in a horizontaldirection or a vertical direction is able to be used as the stretchingmachine. In addition, examples of a tenter type stretching machineinclude a horizontally monoaxially stretching machine, a simultaneouslybiaxially stretching machine, and the like, but is not particularlylimited insofar as a long film is able to be continuously subjected toan inclined stretching treatment, and various types of stretchingmachines are able to be used.

For example, methods disclosed in JP1975-83482A (JP-S50-83482A),JP1990-113920A (JP-H02-113920A), JP1991-182701A (JP-H03-182701A),JP2000-9912A, JP2002-86554A, JP2002-22944A, and WO2007/111313A are ableto be used as a method of the inclined stretching.

When the λ/4 plate includes the optical anisotropic layer or the like onthe support body formed of the polymer film, other layers are laminatedon the support body, and thus a desired λ/4 function is obtained. Theconfiguration material of the optical anisotropic layer is notparticularly limited, and the optical anisotropic layer is formed of acomposition containing a liquid crystal compound, and the opticalanisotropic layer may be a layer exhibiting optical anisotropy which isexpressed by aligning molecules of the liquid crystal compound, may be alayer having optical anisotropy expressed by aligning polymers in apolymer film by stretching the polymer film, or may include both of thelayers. That is, the optical anisotropic layer is able to be configuredof one or two or more biaxial films, and is able to be configured of acombination of two or more monoaxial films such as a combination of a Cplate and an A plate. Naturally, the optical anisotropic layer is alsoable to be configured of a combination of one or more biaxial films andone or more monoaxial films.

In particular, the retardation film in which R₄₅₀/R₅₅₀ is 1.00 to 1.05,for example, is able to be formed by using a polymer of which anabsorption end is in the vicinity of a wavelength of 200 nm, such as apolyolefin-based polymer, a polyvinyl alcohol-based polymer, a celluloseacetate-based polymer, a polyvinyl chloride-based polymer, and apolymethyl methacrylate-based polymer.

In addition, the retardation film in which R₄₅₀/R₅₅₀ is 1.05 to 1.20,for example, is able to be formed by using a polymer of which absorptionend is on a long wavelength side from 200 nm, such as apolycarbonate-based polymer, a polyester-based polymer, apolysulfone-based polymer, a polyether sulfone-based polymer, and apolystyrene-based polymer.

On the other hand, a λ/4 plate prepared as a laminated body of thefollowing λ/2 plate and λ/4 plate is also able to be used as the λ/4plate (C) in which Expression (1) is satisfied and λ/4 plate in whichExpression (2) is satisfied, which are used in the aspect (i).

An optical anisotropic layer used as the λ/2 plate and the λ/4 platedescribed above will be described. The retardation film of the presentinvention may include an optical anisotropic layer, the opticalanisotropic layer is able to be formed of one type or a plurality oftypes of curable compositions containing a liquid crystal compound as amain component, a liquid crystal compound having a polymerizable groupis preferable among the liquid crystal compounds, and it is preferablethat the optical anisotropic layer is formed of one type of the curablecompositions described above.

The λ/4 plate used in the λ/4 plate (C) in which Expression (1) issatisfied and the λ/4 plate in which Expression (2) is satisfied may bean optical anisotropic support body having a desired λ/4 function in thesupport body itself, or may include an optical anisotropic layer or thelike on a support body formed of a polymer film. That is, in the lattercase, the other layer is laminated on the support body, and thus adesired λ/4 function is obtained. The configuration material of theoptical anisotropic layer is not particularly limited, and the opticalanisotropic layer may be a layer which is formed of a compositioncontaining a liquid crystal compound and has optical anisotropyexpressed by aligning molecules of the liquid crystal compound, may be alayer which has optical anisotropy expressed by stretching the polymerfilm and by aligning the polymer in the film, or may include both of thelayers. That is, the optical anisotropic layer is able to be configuredof one or two or more biaxial films, and is able to be configured by acombination of two or more monoaxial films such as a combination of a Cplate and an A plate. Naturally, the optical anisotropic layer is alsoable to be configured by combining one or more biaxial films and one ormore monoaxial films.

Here, the “λ/4 plate” which is the λ/4 plate (C) in which Expression (1)is satisfied and the λ/4 plate in which Expression (2) is satisfiedindicates an optical anisotropic layer in which in-plane retardationRe(λ) at a specific wavelength of λ nm satisfies Re(λ)=λ/4. The aboveexpression may be attained at any wavelength (for example, 550 nm) in avisible light region, and in-plane retardation Re(550) at a wavelengthof 550 nm is preferably 115 nm Re(550) 155 nm, and is more preferably120 nm to 145 nm. According to this range, when the λ/4 plate iscombined with the following λ/2 plate, it is possible to reduce lightleakage of reflection light to the extent of being invisible, and thussetting the retardation to be in this range is preferable.

The λ/2 plate used in the λ/4 plate (C) in which Expression (1) issatisfied and the λ/4 plate in which Expression (2) is satisfied may bean optical anisotropic support body having a desired λ/2 function in thesupport body itself, or may include an optical anisotropic layer or thelike on a support body formed of a polymer film. That is, in the lattercase, the other layer is laminated on the support body, and thus adesired λ/2 function is obtained. The configuration material of theoptical anisotropic layer is not particularly limited, and the opticalanisotropic layer may be a layer which is formed of a compositioncontaining a liquid crystal compound and has optical anisotropyexpressed by aligning molecules of the liquid crystal compound, may be alayer which has optical anisotropy expressed by stretching the polymerfilm and by aligning the polymer in the film, or may include both of thelayers. That is, the optical anisotropic layer is able to be configuredof one or two or more biaxial films, and is able to be configured by acombination of two or more monoaxial films such as a combination of a Cplate and an A plate. Naturally, the optical anisotropic layer is alsoable to be configured by combining one or more biaxial films and one ormore monoaxial films.

Here, the “λ/2 plate” which is the λ/4 plate (C) in which Expression (1)is satisfied and the λ/4 plate in which Expression (2) is satisfiedindicates an optical anisotropic layer in which in-plane retardationRe(λ) at a specific wavelength of λ nm satisfies Re(λ)=λ/2. The aboveexpression may be attained at any wavelength (for example, 550 nm) in avisible light region. Further, in the present invention, in-planeretardation Re1 of the λ/2 plate is set to be substantially two timesin-plane retardation Re2 of the λ/4 plate.

Here, the expression “the retardation is substantially two times”indicates Re1=2×Re2±50 nm. Here, Re1=2×Re2±20 nm is preferable, andRe1=2×Re2±10 nm is more preferable. The above expression may be attainedin any wavelength in the visible light region, and is preferablyattained at a wavelength of 550 nm. According to this range, when theλ/2 plate is combined with the λ/4 plate described above, it is possibleto reduce the light leakage of the reflection light to the extent ofbeing invisible, and thus setting the retardation to be in this range ispreferable.

The λ/4 plate (C) is laminated such that the direction of the linearpolarization light which is transmitted through the λ/4 plate (C) isparallel to a transmission axis direction of the backlight sidepolarizing plate.

When the λ/4 plate (C) is a single layer, an angle between the slow axisdirection of the λ/4 plate (C) and the absorption axis direction of thepolarizing plate is 45°.

When the λ/4 plate (C) is a laminated body of the λ/4 plate and the λ/2plate, an angle between the respective slow axis directions and theabsorption axis direction of the polarizing plate has the followingpositional relationship.

When Rth of the λ/2 plate described above at a wavelength of 550 nm hasa negative value, an angle between the slow axis direction of the λ/2plate and the absorption axis direction of the polarizer layer describedabove is preferably in a range of 75°±8°, is more preferably in a rangeof 75°±6°, and is even more preferably in a range of 75°±3°. Further, inthis case, an angle between the slow axis direction of the λ/4 platedescribed above and the absorption axis direction of the polarizer layerdescribed above is preferably in a range of 15°±8°, is more preferablyin a range of 15°±6°, and is even more preferably in a range of 15°±3°.According to the range described above, it is possible to reduce thelight leakage of reflection light to the extent of being invisible, andthus setting the angle to be in this range is preferable.

In addition, when Rth of the λ/2 plate described above at a wavelengthof 550 nm has a positive value, an angle between the slow axis directionof the λ/2 plate and the absorption axis direction of the polarizerlayer described above is preferably in a range of 15°±8°, is morepreferably in a range of 15°±6°, and is even more preferably in a rangeof 15°±3° Further, in this case, an angle between the slow axisdirection of the λ/4 plate described above and the absorption axisdirection of the polarizer layer described above is preferably in arange of 75°±8°, is more preferably in a range of 75°±6°, and is evenmore preferably in a range of 75°±3°. According to the range describedabove, it is possible to reduce the light leakage of reflection light tothe extent of being invisible, and thus setting the angle to be in thisrange is preferable.

The material of the optical anisotropic support body used in the presentinvention is not particularly limited. For example, cellulose acylate, apolycarbonate-based polymer, a polyester-based polymer such aspolyethylene terephthalate or polyethylene naphthalate, an acrylicpolymer such as polymethyl methacrylate, a styrene-based polymer such aspolystyrene or an acrylonitrile-styrene copolymer (an AS resin), and thelike are able to used in various polymer films. In addition, one type ortwo or more types of polymers are selected from polyolefin such aspolyethylene and polypropylene, a polyolefin-based polymer such as anethylene-propylene copolymer, a vinyl chloride-based polymer, anamide-based polymer such as nylon or aromatic polyamide, an imide-basedpolymer, a sulfone-based polymer, a polyether sulfone-based polymer, apolyether ether ketone-based polymer, a polyphenylene sulfide-basedpolymer, a vinylidene chloride-based polymer, a vinyl alcohol-basedpolymer, a vinyl butyral-based polymer, an arylate-based polymer, apolyoxy methylene-based polymer, an epoxy-based polymer, a polymer inwhich the polymers described above are mixed, and the like, a polymerfilm is prepared by using the selected polymer as a main component, andthe polymer film is able to be used for preparing an optical film in acombination where the properties described above are satisfied.

When the λ/2 plate and the λ/4 plate are a laminated body of a polymerfilm (a transparent support body) and an optical anisotropic layer, itis preferable that the optical anisotropic layer includes at least onelayer formed of a composition containing a liquid crystal compound. Thatis, it is preferable that the λ/2 plate and the λ/4 plate are alaminated body of the polymer film (the transparent support body) andthe optical anisotropic layer formed of the composition containing theliquid crystal compound. A polymer film having small optical anisotropymay be used in the transparent support body, and a polymer film in whichoptical anisotropy is expressed due to a stretching treatment or thelike may be used in the transparent support body. It is preferable thatthe support body has light transmittance of greater than or equal to80%.

The type of liquid crystal compound used for forming the opticalanisotropic layer which may be included in the λ/2 plate and the λ/4plate described above is not particularly limited. For example, anoptical anisotropic layer obtained by forming a low molecular liquidcrystal compound in a nematic alignment in a liquid crystal state, andthen by fixing the alignment using optical cross-linkage or thermalcross-linkage and an optical anisotropic layer obtained by forming ahigh molecular liquid crystal compound in a nematic alignment in aliquid crystal state, and then by fixing the alignment using cooling areable to be used. Furthermore, in the present invention, even when theliquid crystal compound is used in the optical anisotropic layer, theoptical anisotropic layer is a layer formed by fixing the liquid crystalcompound using polymerization or the like, and it is not necessary tohave liquid crystalline properties anymore after the liquid crystalcompound is formed into a layer. The polymerizable liquid crystalcompound may be a multifunctional polymerizable liquid crystal, or maybe a monofunctional polymerizable liquid crystal compound. In addition,the liquid crystal compound may be a discotic liquid crystal compound,or may be a rod-like liquid crystal compound.

In general, the liquid crystal compound is classified into a rod-liketype liquid crystal compound and a disk-like type liquid crystalcompound according to the shape. Further, the liquid crystal compoundincludes a low molecular type liquid crystal compound and a highmolecular type liquid crystal compound. In general, the polymerindicates a polymer having a degree of polymerization of greater than orequal to 100 (Polymer Physics—Phase Transition Dynamics, authorized byDOI Masao, Page 2, Iwanami Shoten, 1992). In the present invention, anyliquid crystal compound is able to be used, and it is preferable that arod-like liquid crystal compound or a disk-like liquid crystal compoundis used. Two or more types of the rod-like liquid crystal compounds, twoor more types of the disk-like liquid crystal compounds, or a mixture ofthe rod-like liquid crystal compound and the disk-like liquid crystalcompound may be used. It is more preferable that the optical anisotropiclayer is formed by using a rod-like liquid crystal compound or adisk-like liquid crystal compound having a reactive group, and it iseven more preferable that at least one has two or more reactive groupsin one liquid crystal molecule, from a viewpoint of enabling atemperature change or a humidity change to be reduced. The liquidcrystal compound may be two or more types of mixtures, and in this case,it is preferable that at least one has two or more reactive groups.

For example, rod-like liquid crystal compounds disclosed inJP1999-513019A (JP-H11-513019A) or JP2007-279688A are able to bepreferably used as the rod-like liquid crystal compound, and discoticliquid crystal compounds disclosed in JP2007-108732A or JP2010-244038Aare able to be preferably used as the discotic liquid crystal compound,but the liquid crystal compounds are not limited thereto.

In the optical anisotropic layer described above, it is preferable thatthe molecules of the liquid crystal compound are fixed into any one ofthe alignment states of vertical alignment, horizontal alignment, hybridalignment, and inclination alignment. In order to prepare a phasedifference plate having symmetric view angle dependency, it ispreferable that a disk-like surface of the discotic liquid crystalcompound is substantially vertical to a film surface (the surface of theoptical anisotropic layer), or a long axis of the rod-like liquidcrystal compound is substantially horizontal to the film surface (thesurface of the optical anisotropic layer). The expression “the discoticliquid crystal compound is substantially vertical” indicates that theaverage value of an angle between the film surface (the surface of theoptical anisotropic layer) and the disk-like surface of the discoticliquid crystal compound is in a range of 70° to 90°. The average valueof the angle is more preferably 80° to 90°, and is even more preferably85° to 90°. The expression “the rod-like liquid crystal compound issubstantially horizontal” indicates that an angle between the filmsurface (the surface of the optical anisotropic layer) and a director ofthe rod-like liquid crystal compound is in a range of 0° to 20°. Theangle is more preferably 0° to 10°, and is even more preferably 0° to5°.

When the λ/2 plate and the λ/4 plate described above include the opticalanisotropic layer containing the liquid crystal compound, the opticalanisotropic layer may be only one layer, or may be a laminated body oftwo or more layers of the rod-like liquid crystal compound, two or morelayers of the disk-like liquid crystal compound, or two or more opticalanisotropic layers of a combination of the rod-like liquid crystalcompound and the disk-like liquid crystal compound.

The optical anisotropic layer described above is able to be formed byapplying a coating liquid containing the liquid crystal compound such asthe rod-like liquid crystal compound or the discotic liquid crystalcompound, as necessary, a polymerization initiator described below, analignment control agent, or other additives onto the support body. It ispreferable that the optical anisotropic layer is formed by forming analignment film on the support body, and by applying the coating liquiddescribed above onto the surface of the alignment film.

In the present invention, it is preferable that the compositiondescribed above is applied onto the surface of the alignment film, andthe molecules of the liquid crystal compound are aligned. The alignmentfilm has a function of setting an alignment direction of the liquidcrystal compound, and thus it is preferable that the alignment film isused in order to realize a preferred aspect of the present invention.However, when the liquid crystal compound is aligned, and then thealignment state is fixed, the alignment film has the function of settingthe alignment direction, and thus the alignment film is not an essentialconstituent of the present invention. That is, it is possible to preparethe polarizing plate of the present invention by transferring only theoptical anisotropic layer on the alignment film in which the alignmentstate is fixed onto the polarization layer or the support body.

It is preferable that the alignment film is formed by performing arubbing treatment with respect to a polymer.

Examples of the polymer include a methacrylate-based copolymer, astyrene-based copolymer, polyolefin, polyvinyl alcohol, and modifiedpolyvinyl alcohol disclosed in paragraphs “0022” of the specification ofJP1996-338913A (JP-H08-338913A), poly(N-methylol acryl amide),polyester, polyimide, a vinyl acetate copolymer, carboxy methylcellulose, polycarbonate, and the like. A silane coupling agent is ableto be used as the polymer. A water-soluble polymer (for example,poly(N-methylol acryl amide), carboxy methyl cellulose, gelatin,polyvinyl alcohol, and modified polyvinyl alcohol) is preferable, thegelatin, the polyvinyl alcohol, and the modified polyvinyl alcohol aremore preferable, and the polyvinyl alcohol and the modified polyvinylalcohol are particularly preferable. A treatment method which has beenwidely adopted as a liquid crystal alignment treatment step of an LCD isable to be applied to the rubbing treatment described above. That is, amethod is able to be used in which the surface of the alignment film isaligned by being rubbed with paper or gauze, felt, rubber or nylon, apolyester fiber, and the like in a constant direction. In general, themethod is performed by averagely rubbing a fiber having a homogeneouslength and thickness with fiber-implanted cloth or the likeapproximately several times.

The composition described above is applied onto the surface of thealignment film which is subjected to the rubbing treatment, and themolecules of the liquid crystal compound are aligned. After that, asnecessary, the alignment film polymer reacts with the multifunctionalmonomer contained in the optical anisotropic layer or the alignment filmpolymer is cross-linked by using a cross-linking agent, and thus it ispossible to form the optical anisotropic layer described above.

It is preferable that the film thickness of the alignment film is in arange of 0.1 μm to 10 μm.

The in-plane retardation (Re) of the transparent support body (thepolymer film) supporting the optical anisotropic layer is preferably 0nm to 150 nm, is more preferably 0 nm to 50 nm, and is even morepreferably 0 nm to 10 nm. According to the range described above, it ispossible to reduce the light leakage of the reflection light to theextent of being invisible, and thus setting the retardation to be inthis range is preferable.

In addition, it is preferable that the retardation (Rth) of the supportbody in the thickness direction is selected depending on a combinationwith the optical anisotropic layer which is disposed on or under thesupport body. Accordingly, it is possible to reduce the light leakage ofthe reflection light at the time of being observed from the inclineddirection, and coloring.

Examples of the polymer include a cellulose acylate film (for example, acellulose triacetate film (a refractive index of 1.48), a cellulosediacetate film, a cellulose acetate butyrate film, and a celluloseacetate propionate film), polyolefin such as polyethylene andpolypropylene, a polyester-based resin film such as polyethyleneterephthalate or polyethylene naphthalate, a polyacrylic resin film suchas a polyether sulfone film and a polymethyl methacrylate, apolyurethane-based resin film, a polyester film, a polycarbonate film, apolysulfone film, a polyether film, a polymethyl pentene film, apolyether ketone film, a (meth)acrylonitrile film, polyolefin, a polymerhaving an alicyclic structure (a norbornene-based resin (Arton (aproduct name), manufactured by JSR Corporation), amorphous polyolefin(Zeonex (a product name), manufactured by Zeon Corporation)), and thelike. Among them, the triacetyl cellulose, the polyethyleneterephthalate, and the polymer having an alicyclic structure arepreferable, and the triacetyl cellulose is particularly preferable.

The transparent support body having a thickness of approximately 10 μmto 200 μm is able to be used, and the thickness of the transparentsupport body is preferably 10 _(μ)m to 80 pm, and is more preferably 20μm to 60 μm. In addition, the transparent support body may be formed bylaminating a plurality of transparent support bodies. In order tosuppress external light reflection, it is preferable that the thicknessof the transparent support body is thin, and when the thickness of thetransparent support body is thinner than 10 μm, intensity of the filmdecreases, and thus setting the thickness of the transparent supportbody to be thinner than 10 μm does not tend to be preferable. In orderto enhance adhesion between the transparent support body and a layerdisposed thereon (an adhesive layer, a vertical alignment film, or aphase difference layer), the transparent support body may be subjectedto a surface treatment (for example, a glow discharge treatment, acorona discharge treatment, an ultraviolet (UV) treatment, and a flametreatment). An adhesive layer (an undercoat layer) may be disposed onthe transparent support body. In addition, in order to apply slidabilityin a transportation step or to prevent a back surface from being bondedto the surface after being wound, it is preferable that a transparentsupport body formed by applying a polymer layer in which inorganicparticles having an average particle diameter of approximately 10 nm to100 nm are mixed at a weight ratio of solid contents of 5% to 40% ontoone side of the support body or by cocasting the polymer layer with thesupport body is used as the transparent support body or a longtransparent support body.

Furthermore, in the above description, the λ/2 plate or the λ/4 platewhich is a laminated body structure having the optical anisotropic layerdisposed on the support body is described, but the present invention isnot limited to this aspect, the λ/2 plate and the λ/4 plate may belaminated on one side of one transparent support body, or the λ/2 platemay be laminated on one side of one transparent support body and the λ/4plate may be laminated on the other side of the transparent supportbody. Further, the λ/2 plate or the λ/4 plate may be formed of singlestretched polymer film (the optical anisotropic support body), or may beformed only of the liquid crystal film which is formed of thecomposition containing the liquid crystal compound. A preferred exampleof the liquid crystal film is also identical to the preferred example ofthe optical anisotropic layer described above.

It is preferable that the λ/2 plate and the λ/4 plate described aboveare continuously manufactured in a state of a long film. At this time, aslow axis angle of λ/2 or λ/4 is 15°±8° or 75° with respect to alongitudinal direction of the long film described above. Accordingly, inthe manufacturing of an optical laminated body described below, thelongitudinal direction of the long film described above is allowed to becoincident with a longitudinal direction of a polarizing film, and thusit is possible to bond the films to each other by a roll-to-rollprocess, and it is possible to manufacture a circularly polarizing plateor an elliptically polarizing plate with high accuracy in an axis angleat the time of bonding and high productivity. Furthermore, when theoptical anisotropic layer is formed of the liquid crystal compound, theangle of the slow axis of the optical anisotropic layer is able to beadjusted by a rubbing angle. In addition, when the λ/2 plate or the λ/4plate is formed of the polymer film (the optical anisotropic supportbody) which is subjected to a stretching treatment, the angle of theslow axis is able to be adjusted according to a stretching direction.

Next, the aspect (ii) will be described.

The reflection polarizer (B) used in the aspect (ii) of the first aspectof the optical sheet member of the present invention is a dielectricmultilayer film which has a reflection center wavelength in a wavelengthrange of 430 nm to 480 nm and a peak of reflectivity having a half-valuewidth of less than or equal to 100 nm.

The reflection polarizer (B) used in the aspect (ii) of the secondaspect of the optical sheet member of the present invention is adielectric multilayer film which has a reflection center wavelength in awavelength range of 300 nm to 430 nm and a peak of reflectivity having ahalf-value width of less than or equal to 100 nm.

In FIG. 6 to FIG. 10, an aspect is illustrated in which a dielectricmultilayer film 11 is used as a reflection polarizer 15. However, thepresent invention is not limited by such a specific example, and forconvenience, the dielectric multilayer film 11 is illustrated as alaminated body of three layers in the drawings, but the number oflaminations is able to be suitably changed in order to attain desiredreflectivity.

It is preferable that the dielectric multilayer film used in the aspect(ii) of the first aspect of the optical sheet member of the presentinvention has a reflection center wavelength in a wavelength range of430 nm to 480 nm and has a peak of reflectivity having a half-valuewidth of less than or equal to 100 nm, that is, it is preferable thatthe dielectric multilayer film does not have a peak of reflectivity in avisible light region other than the peak of the reflectivity describedabove.

It is preferable that the dielectric multilayer film used in the aspect(ii) of the second aspect of the optical sheet member of the presentinvention has a reflection center wavelength in a wavelength range of300 nm to 430 nm and a peak of reflectivity having a half-value width ofless than or equal to 100 nm, that is, it is preferable that thedielectric multilayer film does not have a peak of reflectivity in avisible light region other than the peak of the reflectivity describedabove.

It is preferable that the film thickness of the dielectric multilayerfilm used in the aspect (ii) is thin. The film thickness of thedielectric multilayer film used in the aspect (ii) is preferably 5 μm to100 μm, is more preferably 5 μm to 50 μm, and is particularly preferably5 pm to 20 μm.

A manufacturing method of the dielectric multilayer film used in theaspect (ii) is not particularly limited, but the dielectric multilayerfilm is able to be manufactured with reference to methods disclosed inJP3187821B, JP3704364B, JP4037835B, JP4091978B, JP3709402B, JP4860729B,JP3448626B, and the like, and the contents of these publications areincorporated in the present invention. Furthermore, the dielectricmultilayer film indicates a dielectric multilayer reflection polarizingplate or a birefringent interference polarizer of an alternatingmultilayer film.

<Optical Conversion Member (D)>

The first aspect of the optical sheet member of the present inventionincludes an optical conversion member (D) which converts a part of bluelight which is transmitted through the reflection polarizer (B) and isincident on the optical conversion member (D), and has an emissioncenter wavelength in a wavelength range of 430 nm to 480 nm and a peakof emission intensity having a half-value width of less than or equal to100 nm into green light which has an emission center wavelength in awavelength range of 500 nm to 600 nm and a peak of emission intensityhaving a half-value width of less than or equal to 100 nm and red lightwhich has an emission center wavelength in a wavelength range of 600 nmto 700 nm (preferably, in a wavelength range of 600 nm to 650 nm) andhas a peak of emission intensity having a half-value width of less thanor equal to 100 nm, and transmits a part of the blue light as theoptical conversion member (D).

The second aspect of the optical sheet member of the present inventionincludes an optical conversion member (D) which converts a part or allof UV light which is transmitted through the reflection polarizer (B)and is incident on the optical conversion member (D), and has anemission center wavelength in a wavelength range of 300 nm to 430 nm anda peak of emission intensity having a half-value width of less than orequal to 100 nm into blue light which has an emission center wavelengthin a wavelength range of 430 nm to 480 nm and a peak of emissionintensity having a half-value width of less than or equal to 100 nm,green light which has an emission center wavelength in a wavelengthrange of 500 nm to 600 nm and a peak of emission intensity having ahalf-value width of less than or equal to 100 nm, and red light whichhas an emission center wavelength in a wavelength range of 600 nm to 700nm (preferably, in a wavelength range of 600 nm to 650 nm) and a peak ofemission intensity having a half-value width of less than or equal to100 nm.

In the first aspect of the optical sheet member of the presentinvention, it is preferable that the optical conversion member (D)includes a fluorescent material emitting the green light and the redlight described above when the blue light described above is incidentthereon.

In the second aspect of the optical sheet member of the presentinvention, it is preferable that the optical conversion member (D)includes a fluorescent material emitting the blue light, the greenlight, and the red light described above when light having an emissioncenter wavelength in a wavelength range of 300 nm to 430 nm describedabove and a peak of emission intensity having a half-value width of lessthan or equal to 100 nm is incident thereon.

Examples of an inorganic fluorescent material include anyttrium-aluminum-garnet-based yellow fluorescent body, aterbium-aluminum-garnet-based yellow fluorescent body, and the like. Thefluorescent wavelength of the fluorescent material is able to becontrolled by changing the particle diameter of the fluorescent body. Inaddition, fluorescent materials disclosed in JP2010-532005A are able tobe used.

In addition, an organic fluorescent material is also able to be used,and for example, fluorescent materials disclosed in JP2001-174636A,JP2001-174809A, and the like are able to be used.

In the optical sheet member of the present invention, it is preferablethat the optical conversion member (D) including the fluorescentmaterial is a thermoplastic film which is formed by being stretchedafter dispersing quantum dot sheets or quantum dot materials (a quantumdot and a quantum rod), or an adhesive layer in which quantum dotmaterials are dispersed.

In addition, the material used in the optical sheet of the presentinvention which is stretched after dispersing the quantum dot materialsdescribed above is not particularly limited. For example, celluloseacylate, a polycarbonate-based polymer, a polyester-based polymer suchas polyethylene terephthalate or polyethylene naphthalate, an acrylicpolymer such as polymethyl methacrylate, a styrene-based polymer such aspolystyrene or an acrylonitrile-styrene copolymer (an AS resin), and thelike are able to be used as various polymer films. In addition, one ortwo or more polymers are selected from polyolefin such as polyethyleneand polypropylene, a polyolefin-based polymer such as anethylene-propylene copolymer, a vinyl chloride-based polymer, anamide-based polymer such as nylon or aromatic polyamide, an imide-basedpolymer, a sulfone-based polymer, a polyether sulfone-based polymer, apolyether ether ketone-based polymer, a polyphenylene sulfide-basedpolymer, a vinylidene chloride-based polymer, a vinyl alcohol-basedpolymer, a vinyl butyral-based polymer, an arylate-based polymer, apolyoxy methylene-based polymer, an epoxy-based polymer, a polymer inwhich the polymers described above are mixed, and the like, a polymerfilm is prepared by using the selected polymers as a main component, andthe polymer film is able to be used in preparation of an optical sheetin a combination in which the properties described above are satisfied.

When the optical conversion member (D) including the fluorescentmaterial described above is the quantum dot sheet, such a quantum dotsheet is not particularly limited, but known quantum dot sheetsdisclosed in JP2012-169271A, SID'12 DIGEST p.895, JP2010-532005A, andthe like are able to be used, and the contents of these literatures areincorporated in the present invention. In addition, a Quantum DotEnhancement Film (QDEF, manufactured by NanoSys InC.) is able to be usedas such a quantum dot sheet.

When the optical conversion member (D) including the fluorescentmaterial described above is the thermoplastic film formed by beingstretched after dispersing the quantum dot materials, such athermoplastic film is not particularly limited, but known thermoplasticfilms disclosed in JP2001-174636A, JP2001-174809A, and the like are ableto be used, and the contents of these literatures are incorporated inthe present invention. In addition, specific examples of such athermoplastic resin include a cellulose resin such as triacetylcellulose, a polyester resin, a polyether sulfone resin, a polysulfoneresin, a polycarbonate resin, a polyamide resin, a polyimide resin, apolyolefin resin, a (meth)acrylic resin, a cyclic polyolefin resin (anorbornene-based resin), a polyarylate resin, a polystyrene resin, apolyvinyl alcohol resin, and a mixture thereof.

When the optical conversion member (D) including the fluorescentmaterial described above is the adhesive layer in which the quantum dotmaterials are dispersed, such an adhesive layer is not particularlylimited, but known adhesive layers in which quantum dot materials aredispersed which are disclosed in JP2012-169271A, SID'12 DIGEST p.895,JP2001-174636A, JP2001-174809A, JP2010-532005A, and the like are able tobe used.

In the optical sheet member of the present invention, it is preferablethat the optical conversion member emits fluorescent light holding atleast a part of polarization properties of an incidence ray from aviewpoint of enhanced brightness and low power consumption. The quantumdot materials described above are able to be used as the opticalconversion member which is able to emit the fluorescent light holding atleast a part of the polarization properties of the incidence ray. Inaddition, it is preferable that a quantum rod type disclosed innon-patent literature (THE PHYSICAL CHEMISTRY LETTERS 2013, 4, 502-507)is able to be used from a viewpoint of holding the polarizationproperties of the fluorescent light. In the emission of the fluorescentlight holding a part of the polarization properties of the incidenceray, when excitation light at a polarization degree of 99.9% is incidenton the optical conversion member, the polarization degree of thefluorescent light emitted from the optical conversion member is not 0%,and the polarization degree is preferably 10% to 80%, is more preferably80% to 99%, and is even more preferably 99% to 99.9%.

In the optical sheet member of the present invention, it is preferablethat the optical conversion member includes a fluorescent material inwhich light exited from the optical conversion member includes linearpolarization light and circular polarization light from a viewpoint ofenhanced brightness and low power consumption. Examples of thefluorescent material in which the light exited from the opticalconversion member includes the linear polarization light and thecircular polarization light are able to include the quantum dotmaterials described above. In addition, the λ/4 plate (C) used in theaspect (i) described above, in which Expression (1) and Expression (2)are satisfied, is used in the fluorescent material emitting circularpolarization light, and the circular polarization light is convertedinto the linear polarization light, and thus it is possible to realizean optical sheet member which is excellent from a viewpoint of improvedbrightness.

In addition, when the light exited from the optical conversion memberincludes the linear polarization light, it is more preferable that thepolarizing plate on the BL side further includes a linear polarizationreflection polarizer or further includes a linear polarizationreflection polarizer between the polarizing plate described above (thepolarizing plate on the BL side and an absorption type polarizing plate)and the optical conversion member described above, and thus the lightexited from the optical conversion member (the linear polarizationlight) and the transmission axis of the reflection polarizer and the BLside polarizer are coincident with each other from a viewpoint ofenhanced brightness. The linear polarization reflection polarizerdescribed above may function in an entire wavelength region of awavelength range of 300 nm to 780 nm, is preferably a linearpolarization reflection polarizer reflecting at least a part of light ina wavelength range of 300 nm to 500 nm, and is more preferably a linearpolarization reflection polarizer reflecting all of a part of light in awavelength range of 300 nm to 480 nm.

The linear polarization reflection polarizer described above ispreferably a dielectric multilayer film reflecting light in an entirewavelength region of a wavelength range of 300 nm to 780 nm, is morepreferably a dielectric multilayer film reflecting at least a part oflight in a wavelength range of 300 nm to 500 nm, and is particularlypreferably a dielectric multilayer film reflecting (all or a part of)light in at least a wavelength range of 300 nm to 480 nm.

In addition, the linear polarization reflection polarizer describedabove may be a linear polarization reflection polarizer including λ/4plates on both sides of a light reflecting layer which is formed byfixing a cholesteric liquid crystalline phase reflecting light in anentire wavelength region of a wavelength range of 300 nm to 780 nm, ispreferably a linear polarization reflection polarizer including λ/4plates on both sides of a light reflecting layer which is formed byfixing a cholesteric liquid crystalline phase reflecting at least a partof light in a wavelength range of 300 nm to 500 nm, and is morepreferably linear polarization reflection polarizer including λ/4 plateson both sides of a light reflecting layer which is formed by fixing acholesteric liquid crystalline phase reflecting (all or a part of) lightin at least a wavelength range of 300 nm to 480 nm. Among aspects inwhich light exited from an optical conversion member 11 includes linearpolarization light, and the polarizing plate 1 on the BL side furtherincludes a linear polarization reflection polarizer 17, an aspect inwhich the linear polarization reflection polarizer 17 described above isa linear polarization reflection polarizer including the λ/4 plates 12on both sides of the light reflecting layer 14B which is formed byfixing a cholesteric liquid crystalline phase is illustrated in FIG.14-A. Among aspects in which the linear polarization reflectionpolarizer 17 is further included between the BL side polarizing plate 1and the optical conversion member 11, an aspect in which the linearpolarization reflection polarizer 17 described above is a linearpolarization reflection polarizer including the λ/4 plates 12 on bothsides of the light reflecting layer 14B which is formed by fixing acholesteric liquid crystalline phase is illustrated in FIG. 15. Inaddition, FIG. 14-B illustrates an aspect in which the linearpolarization reflection polarizer 17 is replaced by a B narrowbanddielectric multilayer film reflection polarizer or a broadbanddielectric multilayer film reflection polarizer, and the same effect ofthe invention as that of the linear polarizer described above isobtained.

On the other hand, when the light exited from the optical conversionmember includes the circular polarization light, it is more preferablethat the polarizing plate on the BL side further includes a circularpolarization reflection polarizer or includes a circular polarizationreflection polarizer between the polarizing plate described above (thepolarizing plate on the BL side and the absorption type polarizingplate) and the optical conversion member described above from aviewpoint of enhanced brightness. In this case, the reflection polarizermay function in an entire wavelength region of a wavelength range of 300nm to 780 nm, is preferably a circular polarization reflection polarizerreflecting at least a part of light in a wavelength range of 300 nm to500 nm, and is more preferably a circular polarization reflectionpolarizer reflecting all or a part of light in at least a wavelengthrange of 300 nm to 480 nm.

The circular polarization reflection polarizer described above ispreferably a circular polarization reflection polarizer including λ/4plates on both sides of a dielectric multilayer film reflecting light inan entire wavelength region of a wavelength range of 300 nm to 780 nm,is more preferably a circular polarization reflection polarizerincluding λ/4 plates on both sides of a dielectric multilayer filmreflecting at least a part of light in a wavelength range of 300 nm to500 nm, and is particularly preferably a circular polarizationreflection polarizer including λ/4 plates on both sides of a dielectricmultilayer film reflecting (all or a part of) light in at least awavelength range of 300 nm to 480 nm.

In addition, the circular polarization reflection polarizer describedabove may be a circular polarization reflection polarizer including alight reflecting layer which is formed by fixing a cholesteric liquidcrystalline phase functioning in an entire wavelength region of 300 nmto 780 nm, and λ/4 plates arranged between the light reflecting layerand the polarizing plate described above, is preferably a circularpolarization reflection polarizer including a light reflecting layerwhich is formed by fixing a cholesteric liquid crystalline phasereflecting at least a part of light in a wavelength range of 300 nm to500 nm, and λ/4 plates arranged between the light reflecting layer andthe polarizing plate described above, and is more preferably circularpolarization reflection polarizer including a light reflecting layerwhich is formed by fixing a cholesteric liquid crystalline phasereflecting (all or a part of) light in at least a wavelength range of300 nm to 480 nm, and λ/4 plates arranged between the light reflectinglayer and the polarizing plate described above. Among aspects in whichthe light exited from the optical conversion member 11 includes thecircular polarization light, and the polarizing plate 1 on the BL sidefurther includes a circular polarization reflection polarizer 18, anaspect in which the circular polarization reflection polarizer 18described above is a circular polarization reflection polarizerincluding the light reflecting layer 14B which is formed by fixing acholesteric liquid crystalline phase, and the λ/4 plates 12 arrangedbetween the light reflecting layer 14B and the polarizing plate 1described above is illustrated in FIG. 16. Among aspects in which thecircular polarization reflection polarizer 18 is further includedbetween the BL side polarizing plate 1 described above and the opticalconversion member 11 described above, an aspect in which the circularpolarization reflection polarizer 18 described above is a circularpolarization reflection polarizer including the light reflecting layer14B which is formed by fixing a cholesteric liquid crystalline phase,and the λ/4 plates 12 arranged between the light reflecting layer 14Band the polarizing plate 1 described above is illustrated in FIG. 17.

In the optical sheet member of the present invention, it is preferablethat the optical conversion member is pattern-formed at least at everytwo or more types of fluorescent wavelengths from a viewpoint of lightutilization efficiency.

Examples of an aspect in which the optical conversion member ispattern-formed at least at every two or more types of fluorescentwavelengths are able to preferably include the following aspects.

When the optical conversion member is pattern-formed, an organicfluorescent material, an inorganic fluorescent material, and preferablya quantum dot material (for example, R and G) are dispersed in a bindersuch as an acrylic binder and an epoxy-based binder or in a photoresistmaterial, and then is pattern-formed on a base film by using gravureprinting, ink jet printing, or photolithography, and thus is formed intothe shape of a stripe (or a dot) at a line width of less than or equalto a pixel pitch of a liquid crystal panel, and therefore, patternformation of the optical conversion member is able to be realized. Inaddition, the optical sheet member of the present invention using anoptical sheet member having a periodic pattern shape of a fluorescentbody at a pixel pitch is pattern matched according to a CF pixel of theliquid crystal panel, and thus it is possible to improve a lightutilization rate. In alignment of the pattern, it is possible to use analignment panel bonding device and the like which are used for bondingpattern retardation film (FPR) used in a 3D TV. In addition, when asystem enhancing collimating properties of light between a fluorescentbody pattern and a panel pixel (an anisotropic layer of a refractiveindex such as a lens sheet and a fiber lens, a louver, and the like) isused, an effect of enhancing brightness further increases.

In addition, aspects disclosed in JP2010-138523A are also able to bepreferably used as the aspect in which the optical conversion member ispattern-formed at least at every two or more types of fluorescentwavelengths, and the contents disclosed in this publication are alsoincorporated in the present invention.

<Adhesive Layer>

In the optical sheet member of the present invention, it is preferablethat the optical conversion member (D) and the reflection polarizer (B)are laminated in direct contact with each other or through an adhesivelayer.

In the optical sheet member of the present invention, it is preferablethat the polarizing plate, the optical conversion member (D), the λ/4plate (C), and the reflection polarizer (B) are sequentially laminatedin direct contact with each other or through an adhesive layer.

Examples of a method of laminating these members in direct contact witheach other are able to include a method of laminating the members byapplying a member onto the other member.

In addition, the adhesive layer may be arranged between the members.Examples of the adhesive layer used for laminating the opticalanisotropic layer and the polarizing plate include a substance in whicha ratio of a modulus of storage elasticity G′ and a modulus of losselasticity G″ (tanδ=G″/G′) measured by a dynamic viscoelasticitymeasurement device is 0.001 to 1.5, that is, an adhesive agent or asubstance which is easily crept. Examples of an adhesive agent which isable to be used in the present invention include an acrylic adhesiveagent or a polyvinyl alcohol-based adhesive agent, but the presentinvention is not limited thereto.

In the optical sheet member of the present invention, a refractive indexdifference between the reflection polarizer (B) and a layer adjacent tothe reflection polarizer (B) on the polarizing plate side is preferablyless than or equal to 0.15, is more preferably less than or equal to0.10, and is particularly preferably less than or equal to 0.05.Examples of the layer adjacent to the reflection polarizer (B) on thepolarizing plate side are able to include the adhesive layer describedabove.

An adjustment method of the refractive index of such a adhesive layer isnot particularly limited, and methods disclosed in JP1999-223712A(JP-H11-223712A) are able to be used as the adjustment method. Among themethods disclosed in 223712A (JP-H11-223712A), the following aspect isparticularly preferable.

Examples of the adhesive agent used in the adhesive layer describedabove are able to include resins such as a polyester-based resin, anepoxy-based resin, a polyurethane-based resin, a silicone-based resin,and an acrylic resin. These resins may be independently used or two ormore types thereof may be used by being mixed. In particular, theacrylic resin is preferable from a viewpoint of excellent reliabilitysuch as waterproofness, heat resistance, and light resistance, anexcellent adhesion force and transparency, and ease of adjusting arefractive index to be suitable for a liquid crystal display. Examplesof the acrylic adhesive agent are able to include an acrylic acid andester thereof, a methacrylic acid and ester thereof, a homopolymer of anacryl monomer such as acryl amide and acrylonitrile or a copolymerthereof, and a copolymer of at least one type of the acryl monomersdescribed above and an aromatic vinyl monomer such as vinyl acetate, amaleic anhydride, and styrene. In particular, it is preferable that theexamples of the acrylic adhesive agent include a main monomer expressingadhesiveness, such as ethylene acrylate, butyl acrylate, and 2-ethylhexyl acrylate, a monomer which becomes a cohesive component, such asvinyl acetate, acrylonitrile, acryl amide, styrene, methacrylate, andmethyl acrylate, and a copolymer which improves an adhesion force orapplies a starting point of cross-linkage, and is formed of a functionalgroup-containing monomer such as a methacrylic acid, an acrylic acid, anitaconic acid, hydroxy ethyl methacrylate, hydroxy propyl methacrylate,dimethyl amino ethyl methacrylate, acryl amide, methylol acryl amide,glycidyl methacrylate, and maleic anhydride in which glass transitionpoint (Tg) is in a range of −60° C. to −15° C., and a weight averagemolecular weight is in a range of 200,000 to 1,000,000.

As a curing agent, one type or two or more types of a metalchelate-based cross-linking agent, an isocyanate-based cross-linkingagent, an epoxy-based cross-linking agent are used by being mixed, asnecessary. It is practically preferable that such an acrylic adhesiveagent is mixed such that an adhesion force is in a range of 100 g/25 mmto 2,000 g/25 mm in a state of containing fillers described below. Whenthe adhesion force is less than 100 g/25 mm, environment resistancedeteriorates, and in particular, peeling off may occur at hightemperature and high humidity, whereas when the adhesion force isgreater than 2000 g/25 mm, rebonding is not able to be performed, andeven when the rebonding is able to be performed, the adhesive agent mayremain. The refractive index of the acrylic adhesive agent (B method inJIS K-7142) is preferably in a range of 1.45 to 1.70, and isparticularly preferably in a range of 1.5 to 1.65.

The fillers for adjusting the refractive index are contained in theadhesive agent. Examples of the fillers are able to include an inorganicwhite pigment such as silica, calcium carbonate, aluminum hydroxide,magnesium hydroxide, clay, talc, and titanium dioxide, an organictransparent or white pigment such as an acrylic resin, a polystyreneresin, a polyethylene resin, an epoxy resin, and a silicone resin, andthe like. When the acrylic adhesive agent is selected, silicone beadsand epoxy resin beads are preferable from a viewpoint of havingexcellent dispersion properties with respect to the acrylic adhesiveagent and of obtaining an excellent and homogeneous refractive index. Inaddition, it is preferable that the fillers are spherical fillers havinghomogeneous light diffusion.

The particle diameter of such fillers (JIS B9921) is preferably 0.1 μmto 20.0 μm, and is more preferably in a range of 1.0 μm to 10.0 μm. Inparticular, the particle diameter of the fillers is preferably in arange of 0.5 μm to 10 μm.

In the present invention, the refractive index of the filler (B methodin JIS K-7142) preferably has a difference of 0.05 to 0.5 with respectto the refractive index of the adhesive agent, and more preferably has adifference of 0.05 to 0.3.

The content of the fillers in the diffusion adhesive layer is 1.0 mass %to 40.0 mass %, and in particular, is preferably 3.0 mass % to 20 mass%.

[Image Display Device]

A first aspect of the image display device of the present inventionincludes the optical sheet member of the first aspect of the presentinvention and the backlight unit, a backlight unit includes a lightsource emitting blue light which has an emission center wavelength in awavelength range of 430 nm to 480 nm and a peak of emission intensityhaving a half-value width of less than or equal to 100 nm, and thebacklight unit includes a reflection member which converts apolarization state of light emitted from the light source and reflectedon the optical sheet member and reflects the light in a rear portion ofthe light source.

A second aspect of the image display device of the present inventionincludes the optical sheet member of the second aspect of the presentinvention and a backlight unit, the backlight unit includes a lightsource emitting UV light which has an emission center wavelength in awavelength range of 300 nm to 430 nm and a peak of emission intensityhaving a half-value width of less than or equal to 100 nm, and thebacklight unit includes a reflection member which converts apolarization state of light emitted from the light source and reflectedon the optical sheet member and reflects the light in a rear portion ofthe light source.

When directivity of a light ray of the light source is high (the lightis condensed on a front surface), a difference between a wavelengthapplying a peak of light emitting intensity of the blue light or the UVlight of the backlight unit and a wavelength applying a peak ofreflectivity of the brightness enhancement film may not exist, but whenthe directivity of the light source is low (a diffusion light sourcehaving low light condensing properties), the difference is preferably 0nm to 100 nm, is more preferably 5 nm to 70 nm, and is even morepreferably 10 nm to 50 nm, in consideration of a shortwave shift in areflection band in an inclined direction of the reflection polarizer.

<Backlight Unit>

The configuration of the backlight unit may be an edge light mode inwhich a light guide plate, a reflection plate, or the like is used as aconfiguration member, or may be a direct backlight mode, and it ispreferable that the backlight unit includes the reflection member in therear portion of the light source, which converts the polarization stateof the light emitted from the light source and reflected on the opticalsheet member and reflects the light. Such a reflection member is notparticularly limited, but known reflection members disclosed inJP3416302B, JP3363565B, JP4091978B, JP3448626B, and the like are able tobe used as the reflection member, and the contents of the publicationsare incorporated in the present invention.

In the first aspect of the image display device of the presentinvention, it is preferable that the light source of the backlight unitincludes a blue light emitting diode emitting the blue light describedabove.

In the second aspect of the image display device of the presentinvention, it is preferable that the light source of the backlight unitincludes an UV light emitting diode emitting UV light.

In the first aspect of the image display device of the presentinvention, it is preferable that the backlight unit includes awavelength selective filter for a blue color which selectively transmitslight having a wavelength shorter than 460 nm among the blue light rays.

Such a wavelength selective filter for a blue color is not particularlylimited, but known wavelength selective filters for a blue colordisclosed in JP2008-52067A and the like are able to be used, and thecontents of this publication are incorporated in the present invention.

In addition, it is preferable that the backlight unit includes a knowndiffusion plate or diffusion sheet, a prism sheet (for example, BEF andthe like), and a light guide device. Examples of other members includemembers disclosed in JP3416302B, JP3363565B, JP4091978B, JP3448626B, andthe like, and the contents of the publications are incorporated in thepresent invention.

In addition, the directivity of the light source is controlled byincluding the diffusion sheet and the prism sheet (for example, the BEFand the like) between the optical sheet member and the liquid crystalpanel backlight side polarizing plate of the present invention, and thusit is possible to prepare a preferred image display device.

<Display Panel>

Examples of the image display device described above are able to includea liquid crystal display (LCD), a plasma display (PDP), anelectroluminescence display (OELD or IELD), a field emission display(FED), a touch panel, electronic paper, and the like.

A preferred example of a display panel of the image display device is atransmissive mode liquid crystal panel, and the panel includes a liquidcrystal cell between a pair of polarizers. In general, a retardationfilm for compensating a view angle is arranged between each of thepolarizers and the liquid crystal cell. The configuration of the liquidcrystal cell is not particularly limited, and a liquid crystal cellhaving a general configuration is able to be adopted. The liquid crystalcell, for example, includes a pair of substrates which are arranged toface each other, and a liquid crystal layer interposed between the pairof substrates, and as necessary, may include a color filter layer andthe like. The driving mode of the liquid crystal cell is notparticularly limited, and various modes such as a twisted nematic (TN)mode, a super twisted nematic (STN) mode, a vertical alignment (VA)mode, an in-plane switching (IPS) mode, and an optically compensatedbend cell (OCB) mode are able to be used.

It is preferable that the liquid crystal cell used in the image displaydevice having a liquid crystal panel of the present invention is in a VAmode, an OCB mode, an IPS mode, or a TN mode, but the present inventionis not limited thereto.

In the liquid crystal cell of the TN mode, rod-like liquid crystalmolecules are substantially horizontally aligned at the time of notapplying a voltage, and are twistedly aligned by 60° to 120°. The liquidcrystal cell of the TN mode is mostly used as a color TFT liquid crystaldisplay device, and is disclosed in a plurality of literatures.

In the liquid crystal cell of the VA mode, the rod-like liquid crystalmolecules are substantially vertically aligned at the time of notapplying a voltage. The liquid crystal cell of the VA mode includes (1)a liquid crystal cell of a VA mode in the narrow sense in which rod-likeliquid crystal molecules are substantially vertically aligned at thetime of not applying a voltage, and are substantially horizontallyaligned at the time of applying a voltage (disclosed in JP1990-176625A(JP-H02-176625A)), (2) a liquid crystal cell for widening a view anglein which a VA mode is a multidomain (an MVA mode) (disclosed in SID97,Digest of tech. Papers (Proceedings) 28 (1997) 845), (3) a liquidcrystal cell of a mode (an n-ASM mode) in which rod-like liquid crystalmolecules are substantially vertically aligned at the time of notapplying a voltage, and are twistedly multidomain-aligned at the time ofapplying a voltage (disclosed in Proceedings of Japan Liquid CrystalConference 58 to 59 (1998)), and (4) a liquid crystal cell of a SURVIVALmode (published in LCD International 98). In addition, the liquidcrystal cell may be any one of a Patterned Vertical Alignment (PVA) typeliquid crystal cell, an Optical Alignment type liquid crystal cell, anda Polymer-Sustained Alignment (PSA) liquid crystal cell. The details ofthese modes are specifically disclosed in JP2006-215326A andJP2008-538819A.

In the liquid crystal cell of the IPS mode, the rod-like liquid crystalmolecules are aligned to be substantially parallel to the substrate, andan electric field which is parallel to the surface of the substrate isapplied, and thus the liquid crystal molecule planarly responds. In theIPS mode, black display is performed in a state of not applying anelectric field, and the absorption axes of a pair of upper and lowerpolarizing plates are orthogonal to each other. Methods in which leakedlight in the inclined direction at the time of the black display isreduced by using the optical compensate sheet, and thus a view angle isimproved are disclosed in JP1998-54982A (JP-H10-54982A), JP1999-202323A(JP-H11-202323A), JP1997-292522A (JP-H09-292522A), JP1999-133408A(JP-H11-133408A), JP1999-305217A (JP-H11-305217A), JP1998-307291A(JP-H10-307291A), and the like.

It is preferable that an embodiment of the liquid crystal display deviceincludes a liquid crystal cell in which a liquid crystal layer isinterposed between facing substrates of which at least one includes anelectrode, and the liquid crystal cell is configured by being arrangedbetween two polarizing plates. The liquid crystal display deviceincludes the liquid crystal cell in which a liquid crystal is sealedbetween upper and lower substrates, changes the alignment state of theliquid crystal by applying a voltage, and thus displays an image.Further, as necessary, the liquid crystal display device includes anassociated functional layer such as a polarizing plate protective filmor an optical compensate member performing optical compensation, and anadhesive layer. In addition, the image display device of the presentinvention may include other members. For example, a surface layer suchas a forward scattering layer, a primer layer, an antistatic layer, andan undercoat layer may be arranged along with (or instead of) a colorfilter substrate, a thin layer transistor substrate, a lens film, adiffusion sheet, a hard coat layer, an antireflection layer, a lowreflection layer, an antiglare layer, and the like.

In FIG. 11, an example of a configuration of a case where the firstaspect of the image display device of the present invention is a liquidcrystal display device is illustrated. In FIG. 11, an image displaydevice 51 is formed by laminating the backlight unit 31, the opticalsheet member 21 of the present invention (a laminated body of thebrightness enhancement film 11 and the backlight side polarizing plate1), a thin layer transistor substrate 41, a liquid crystal cell 42, acolor filter substrate 43, and a display side polarizing plate 44 inthis order.

Furthermore, the configuration of the optical sheet member 21 of thepresent invention is illustrated in FIG. 11 by using the configurationof FIG. 2 as a representative example, but the image display device ofthe present invention is not limited to the configuration of FIG. 11 bysuch an example.

(Color Filter)

When the light source uses visible B of less than or equal to 500 nm, apixel in the present invention is able to be formed by using variousknown methods as a method of forming an RGB pixel. For example, aphotomask is able to be formed on a glass substrate, a desired blackmatrix is able to be formed thereon by using the photoresist, and apixel pattern of R, G, B is able to be formed thereon, and an inkcomposition is discharged by using a printing device of an ink jetmethod until a desired concentration is obtained in a region (a concaveportion surrounded by a convex portion) which is partitioned by a blackmatrix having a predetermined width and a black matrix having a widthwider than that of the black matrix described above at every n blackmatrices by using a coloring ink for a pixel of R, G, and B, and thus acolor filter formed of the pattern of R, G, and B is able to beprepared. After image coloring, each pixel and the black matrix may becompletely cured by baking or the like.

Preferred properties of the color filter are disclosed in JP2008-083611Aand the like, and the contents of the publications are incorporated inthe present invention.

For example, it is preferable that one wavelength at which thetransmittance is half of the maximum transmittance in a color filterexhibiting a green color is greater than or equal to 590 nm and lessthan or equal to 610 nm, and the other is greater than or equal to 470nm and less than or equal to 500 nm. In addition, it is preferable thatone wavelength at which the transmittance is half of the maximumtransmittance described above in the color filter exhibiting a greencolor is greater than or equal to 590 nm and less than or equal to 600nm. Further, it is preferable that the maximum transmittance of thecolor filter exhibiting a green color is greater than or equal to 80%.It is preferable that a wavelength at which the transmittance is themaximum transmittance in the color filter exhibiting a green color isgreater than or equal to 530 nm and less than or equal to 560 nm.

In the light source of the light source unit described above, it ispreferable that the wavelength of a light emitting peak in a wavelengthregion of greater than or equal to 600 nm and less than or equal to 700nm is greater than or equal to 620 nm and less than or equal to 650 nm.The light source of the light source unit described above has a lightemitting peak in a wavelength region of greater than or equal to 600 nmand less than or equal to 700 nm, and in the color filter exhibiting agreen color, it is preferable that the transmittance at the wavelengthof the light emitting peak described above is less than or equal to 10%of the maximum transmittance.

In the color filter exhibiting the red color described above, it ispreferable that the transmittance at a wavelength of greater than orequal to 580 nm and less than or equal to 590 nm is less than or equalto 10% of the maximum transmittance.

As the pigment for a color filter, in a blue color, a complementarypigment C.I. Pigment Violet 23 is used in C.I. Pigment Blue 15:6. In ared color, C.I. Pigment Yellow 139 is used in C.I. Pigment Red 254 as apigment for a complementary color. As the pigment for a green color, ingeneral, C.I. Pigment Yellow 150, C.I. Pigment Yellow 138, and the likeare used in C.I. Pigment Green 36 (copper bromide phthalocyanine green)and C.I. Pigment Green 7 (copper chloride phthalocyanine green) as apigment for a complementary color. These pigments are able to becontrolled by adjusting the composition of the pigment. The compositionof the complementary pigment is increased by a small amount with respectto a comparative example, and thus it is possible to set a half-valuewavelength on the long wavelength side to be in a range of 590 nm to 600nm. Furthermore, currently, the pigment is generally used, but a colorfilter of a dye may be used insofar as the pigment is able to control aspectrum and to ensure process stability and reliability.

(Black Matrix)

In the image display device of the present invention, the black matrixis arranged between the respective pixels. Examples of a materialforming a black stripe include a material using a sputtered film ofmetal such as chromium, a light shielding photosensitive composition inwhich a photosensitive resin, a black coloring agent, and the like arecombined, and the like. Specific examples of the black coloring agentinclude carbon black, titanium carbon, iron oxide, titanium oxide,graphite, and the like, and among them, the carbon black is preferable.

(Thin Layer Transistor)

It is preferable that the image display device of the present inventionfurther includes a TFT substrate including a thin layer transistor(hereinafter, referred to as a TFT).

It is preferable that the thin layer transistor described above includesan oxide semiconductor layer having a carrier concentration of less than1×10¹⁴/cm³. A preferred aspect of the thin layer transistor describedabove is disclosed in JP2011-141522A, and the contents of thepublication are incorporated in the present invention.

<Method of Bonding Optical Sheet Member to Image Display Device>

A known method is able to be used as a method of bonding the opticalsheet member of the present invention to the image display device suchas a liquid crystal display device. In addition, a roll-to-panelmanufacturing method is able to be used, and the roll-to-panelmanufacturing method is preferable from a viewpoint of improvingproductivity and yield. The roll-to-panel manufacturing method isdisclosed in JP2011-48381A, JP2009-175653A, JP4628488B, JP4729647B,WO2012/014602A, WO2012/014571A, and the like, but the present inventionis not limited thereto.

Examples

Hereinafter, the characteristics of the present invention will be morespecifically described with reference to examples and comparativeexamples. Materials, used amounts, ratios, treatment contents, treatmentsequences, and the like of the following examples are able to besuitably changed unless the changes cause deviance from the gist of thepresent invention. Therefore, the range of the present invention willnot be restrictively interpreted by the following specific examples.

Manufacturing Example 1

<Preparation of Polarizing Plate>

A retardation film was prepared by using a commercially availablecellulose acylate-based film “TD60” (manufactured by FujifilmCorporation) as a front-side polarizing plate protective film of abacklight side polarizing plate.

A commercially available cellulose acylate-based film “TD60”(manufactured by Fujifilm Corporation) was used as a rear-sidepolarizing plate protective film of the backlight side polarizing plate,and a thinner optical sheet member was able to be prepared by using acellulose acylate-based film having a thickness of preferably less thanor equal to 40 μm, and more preferably less than or equal to 25 μm.

As described in “0219” to “0220” of JP2006-293275A, a polarizer wasmanufactured, and the retardation film and the polarizing plateprotective film described above were bonded to both surfaces of thepolarizer, and thus a polarizing plate was manufactured. In addition,when the optical member sheet of the present invention is bonded to thepolarizing plate, a part or all of the optical member sheet such as aλ/4 plate is able to function as a protective film on one side of thepolarizing plate.

Manufacturing Example 2

<Preparation of Polarizing Plate>

A polarizing plate was manufactured by bonding the retardation film andthe polarizing plate protective film onto both surfaces of thepolarizer, respectively, by the same method as that in ManufacturingExample 1 except that a long film 1 having a thickness of 40 μm obtainedby supplying a pellet of a mixture [Tg of 127° C.] of 90 parts by massof an acrylic resin having a lactone ring structure {a copolymerizationmonomer mass ratio=methyl methacrylate/methyl 2-(hydroxymethyl)acrylate=8/2, a lactone ring formation rate of approximately 100%, acontent ratio of the lactone ring structure of 19.4%, a weight averagemolecular weight of 133000, a melt flow rate of 6.5 g/10 minutes (240°C. and 10 kgf), and Tg of 131° C.} and 10 parts by mass of anacrylonitrile-styrene (AS) resin {Toyo AS AS20, manufactured byToyo-Styrene Co., Ltd.} to a biaxial extruder, and by melting andextruding the pellet at approximately 280° C. into the shape of a sheetwas used as the rear side polarizing plate protective film of thebacklight side polarizing plate.

Manufacturing Example 3

<Preparation of Polarizing Plate>

A polarizing plate was manufactured by bonding the retardation film andthe polarizing plate protective film onto both surfaces of thepolarizer, respectively, by the same method as that in ManufacturingExample 1 except that a commercially available COP film “Zeonor ZF14”(manufactured by Zeon Corporation) was used as the rear side polarizingplate protective film of the backlight side polarizing plate.

Example 1-A

<Formation of Optical Conversion Member>

A quantum dot sheet (a quantum dot material (G,R)) which emittedfluorescent light of green light having a center wavelength of 540 nmand a half-value width of 40 nm and red light having a center wavelengthof 645 nm and a half-value width of 30 nm when blue light of a bluelight emitting diode was incident thereon was formed as the opticalconversion member with reference to JP2012-169271A.

The obtained quantum dot sheet and the polarizing plate 1 manufacturedin Manufacturing Example 1 described above were arranged through an airlayer.

<Formation of B Narrowband λ/4 Plate>

A second λ/4 plate (a B narrowband λ/4 plate) was prepared on acommercially available cellulose acylate-based film “TD60” (manufacturedby Fujifilm Corporation) by using a discotic liquid crystal withreference to JP2012-108471A.

In the obtained second λ/4 plate, that is, the B narrowband λ/4 plate,Re(450) was 112 nm, Re(550) was 93 nm, and the film thickness includingTAC was approximately 60 μm.

<Formation of Reflection Polarizer>

A light reflecting layer formed by fixing a cholesteric liquidcrystalline phase was formed on the B narrowband λ/4 plate describedabove according to direct coating by changing the added amount of achiral agent used with reference to JP2013-203827A (disclosed in “0016”to “0148”) and Fuji Film Research & Development No.50 (2005) pp.60 to63.

In the obtained light reflecting layer, the reflection center wavelengthof the peak of the maximum reflectivity was 445 nm, the half-value widthwas 70 nm, the film thickness was 2.5 μm, An of the liquid crystal was0.12, and the average refractive index was 1.57. In addition, when thelight reflecting layer having An of the liquid crystal of 0.17 was used,the reflection center wavelength of 450 nm, the half-value width of 100nm, and the film thickness of 2.5 μm were able to be realized.

As described above, a laminated body in which the polarizing plate, theoptical conversion member (the quantum dot sheet), the B narrowband λ/4plate+a cholesteric reflection polarizer were laminated through an airlayer was an optical sheet member of Example 1-A.

<Manufacturing of Liquid Crystal Display Device>

A liquid crystal display device (a product name of KDL-46W900A,manufactured by Sony Corporation) including a commercially availablequantum dot type backlight was used, the optical sheet member of Example1-A was used as the backlight side polarizing plate, the TV describedabove was disassembled, a quantum dot (a glass enclosed bar type quantumdot) was extracted, the quantum dot type backlight was changed to a Bnarrowband (450 nm) backlight unit, and thus a liquid crystal displaydevice of Example 1-A was manufactured.

The B narrowband backlight unit included a blue light emitting diode(Blue, a main wavelength of 450 nm, and a half-value width of 20 nm) asa light source. In addition, the B narrowband backlight unit included areflection member which converted a polarization state of light emittedfrom the light source and reflected on the optical sheet member andreflected the light in a rear portion of the light source.

Example 1

<Formation of Optical Conversion Member>

A quantum dot sheet (a quantum dot material (G,R)) which emittedfluorescent light of green light having a center wavelength of 540 nmand a half-value width of 40 nm and red light having a center wavelengthof 645 nm and a half-value width of 30 nm when blue light of a bluelight emitting diode was incident thereon was formed as the opticalconversion member with reference to JP2012-169271A.

The obtained quantum dot sheet and the polarizing plate 1 manufacturedin Manufacturing Example 1 described above were bonded to each other byusing an acrylic adhesive agent having a refractive index of 1.47.

<Formation of B Narrowband λ/4 Plate>

A B narrowband λ/4 plate was prepared with reference to JP2012-108471A.

In the obtained B narrowband λ/4 plate, Re(450) was 112 nm, Re(550) was93 nm, and the film thickness was 60 μm.

The obtained B narrowband λ/4 plate and the optical conversion membermanufactured as described above were bonded to each other by using anacrylic adhesive agent having a refractive index of 1.47.

<Formation of Reflection Polarizer>

A light reflecting layer formed by fixing a cholesteric liquidcrystalline phase was formed on a support body with coating by changingthe added amount of a chiral agent used with reference to JP2013-203827A(disclosed in “0016” to “0148”) and Fuji Film Research & DevelopmentNo.50 (2005) pp.60 to 63.

In the obtained light reflecting layer, the reflection center wavelengthof the peak of the maximum reflectivity was 445 nm, the half-value widthwas 70 nm, the film thickness was 2.5 μm, An of the liquid crystal was0.12, and the average refractive index was 1.57. In addition, when thelight reflecting layer having An of the liquid crystal of 0.17 was used,the reflection center wavelength of 450 nm, the half-value width of 100nm, and the film thickness of 2.5 μm were able to be realized.

Only the light reflecting layer formed as described above was peeled offfrom the support body, and was transferred onto the obtained Bnarrowband λ/4 plate.

The total thickness of a brightness enhancement film including theobtained quantum dot sheet, the B narrowband λ/4 plate, and thereflection polarizer was 2.5 μm.

Thus, a laminated body of the obtained polarizing plate and thebrightness enhancement film was an optical sheet member of Example 1.

<Manufacturing of Liquid Crystal Display Device>

A commercially available liquid crystal display device (a product nameof TH-L42D2, manufactured by Panasonic Corporation) was disassembled,the optical sheet member of Example 1 was used as the backlight sidepolarizing plate, and a backlight unit was changed to the following Bnarrowband backlight unit, and thus a liquid crystal display device ofExample 1 was manufactured.

The used B narrowband backlight unit included a blue light emittingdiode (B-LED manufactured by Nichia Corporation: Blue, a main wavelengthof 465 nm, and a half-value width of 20 nm) as a light source. Inaddition, the B narrowband backlight unit included a reflection memberwhich converted a polarization state of light emitted from the lightsource and reflected on the optical sheet member described above andreflected the light in a rear portion of the light source.

Example 2-A

<Formation of Optical Conversion Member>

A quantum dot sheet (a quantum dot material (B,G,R)) which emittedfluorescent light of blue light having a center wavelength of 460 nm anda half-value width of 40 nm, green light having a center wavelength of560 nm and a half-value width of 40 nm, and red light having a centerwavelength of 610 nm and a half-value width of 40 nm when UV light of anUV light emitting diode was incident thereon was formed by using aquantum dot “Lumidot (registered trademark)” manufactured by NanocoTechnologies Limited and distributed by Sigma-Aldrich Corporation as theoptical conversion member.

<Formation of UV Narrowband λ/4 Plate>

An UV narrowband λ/4 plate using a COP material which was not absorbedin an UV range was prepared with reference to JP2003-270435A.

In the obtained UV narrowband λ/4 plate, Re(380) was 95 nm, Re(450) was95 nm, and the film thickness was 40 μm.

<Formation of Reflection Polarizer>

One light reflecting layer formed by fixing a cholesteric liquidcrystalline phase was formed on the λ/4 plate described above withdirect coating by changing the added amount of a chiral agent used withreference to JP2013-203827A (disclosed in “0016” to “0148”) and FujiFilm Research & Development No.50 (2005) pp.60 to 63.

In the obtained light reflecting layer, the reflection center wavelengthof the peak of the maximum reflectivity was 385 nm, the half-value widthwas 70 nm, the film thickness was 2.5 μm, and the average refractiveindex was 1.57.

The total thickness of a brightness enhancement film including theobtained UV narrowband λ/4 plate and the reflection polarizer was 43 μm.

Thus, a laminated body formed by laminating the obtained quantum dotsheet, the polarizing plate 1 manufactured in Manufacturing Example 1described above, and the brightness enhancement film through an airlayer was an optical sheet member of Example 2-A.

<Manufacturing of Liquid Crystal Display Device>

A commercially available liquid crystal display device (a product nameof TH-L42D2, manufactured by Panasonic Corporation) was disassembled,the optical sheet member of Example 2-A was used as the backlight sidepolarizing plate, and a backlight unit was changed to the following UVnarrowband backlight unit, and thus a liquid crystal display device ofExample 2-A was manufactured.

The used UV narrowband backlight unit included an UV light emittingdiode (UV-LED manufactured by Nichia Corporation: NC4U133A, a mainwavelength of 365 nm, and a half-value width of 9 nm) as a light source.In addition, the UV narrowband backlight unit included a reflectionmember which converted a polarization state of light emitted from thelight source and reflected on the optical sheet member described aboveand reflected the light in a rear portion of the light source.

Furthermore, the obtained liquid crystal display device of Example 2-Aincluded a thin layer transistor which included an oxide semiconductorlayer having a carrier concentration of less than 1×10¹⁴/cm³.

Example 2

<Formation of Optical Conversion Member>

A quantum dot sheet (a quantum dot material (B,G,R)) which emittedfluorescent light of blue light having a center wavelength of 460 nm anda half-value width of 40 nm, green light having a center wavelength of560 nm and a half-value width of 40 nm, and red light having a centerwavelength of 610 nm and a half-value width of 40 nm when UV light of anUV light emitting diode was incident thereon was formed by using aquantum dot “Lumidot (registered trademark)” manufactured by NanocoTechnologies Limited and distributed by Sigma-Aldrich Corporation as theoptical conversion member.

The obtained quantum dot sheet and the polarizing plate 1 manufacturedin Manufacturing Example 1 described above were bonded to each other byusing an acrylic adhesive agent having a refractive index of 1.47.

<Formation of UV Narrowband λ/4 Plate>

An UV narrowband λ/4 plate using a COP material which was not absorbedin an UV range was prepared with reference to JP2003-270435A.

In the obtained UV narrowband λ/4 plate, Re(380) was 95 nm, Re(450) was95 nm, and the film thickness was 40 μm.

The obtained UV narrowband λ/4 plate and the optical conversion membermanufactured as described above were bonded to each other by using anacrylic adhesive agent having a refractive index of 1.47.

<Formation of Reflection Polarizer>

One light reflecting layer formed by fixing a cholesteric liquidcrystalline phase was formed on a support body with coating by changingthe added amount of a chiral agent used with reference to JP2013-203827A(disclosed in “0016” to “0148”) and Fuji Film Research & DevelopmentNo.50 (2005) pp.60 to 63.

In the obtained light reflecting layer, the reflection center wavelengthof the peak of the maximum reflectivity was 385 nm, the half-value widthwas 70 nm, the film thickness was 2.5 μm, and the average refractiveindex was 1.57.

Only the light reflecting layer formed as described above was peeled offfrom the support body, and was transferred onto the obtained UVnarrowband λ/4 plate.

The total thickness of a brightness enhancement film including theobtained UV narrowband λ/4 plate and the reflection polarizer was 43 μm.

Thus, a laminated body of the obtained polarizing plate and thebrightness enhancement film was an optical sheet member of Example 2.

<Manufacturing of Liquid Crystal Display Device>

A commercially available liquid crystal display device (a product nameof TH-L42D2, manufactured by Panasonic Corporation) was disassembled,the optical sheet member of Example 2-A was used as the backlight sidepolarizing plate, and a backlight unit was changed to the following UVnarrowband backlight unit, and thus a liquid crystal display device ofExample 2 was manufactured.

The used UV narrowband backlight unit included an UV light emittingdiode (UV-LED manufactured by Nichia Corporation: NC4U133A, a mainwavelength of 365 nm, and a half-value width of 9 nm) as a light source.In addition, the UV narrowband backlight unit included a reflectionmember which converted a polarization state of light emitted from thelight source and reflected on the optical sheet member and reflected thelight in a rear portion of the light source.

Furthermore, the obtained liquid crystal display device of Example 2included a thin layer transistor which included an oxide semiconductorlayer having a carrier concentration of less than 1×10¹⁴/cm³.

Example 3

An optical sheet member of Example 3 was manufactured by the same methodas that in Example 1 except that the thickness of the brightnessenhancement film was changed as shown in Table 1 described below bychanging the thickness of the cholesteric layer in Example 1.

After that, a liquid crystal display device of Example 3 wasmanufactured by the same method as that in Example 1 except that theoptical sheet member of Example 3 was used instead of the optical sheetmember of Example 1, and the light source of the backlight was changedto B-LED manufactured by Nichia Corporation (Royal Blue, a mainwavelength of 445 nm, and a half-value width of 20 nm) in themanufacturing of the liquid crystal display device of Example 1.

Example 4

An optical sheet member of Example 4 was manufactured by the same methodas that in Example 2 except that the thickness of the brightnessenhancement film was changed as shown in Table 1 described below bychanging the thickness of the λ/4 layer in Example 2.

After that, a liquid crystal display device of Example 4 wasmanufactured by the same method as that in Example 2 except that theoptical sheet member of Example 4 was used instead of the optical sheetmember of Example 2, and the light source of the backlight was changedto UV-LED manufactured by Nichia Corporation (NC4U134A, a mainwavelength of 385 nm, and a half-value width of 10 nm) in themanufacturing of the liquid crystal display device of Example 2.

Example 5

An optical sheet member of Example 5 was manufactured by the same methodas that in Example 1 except that the polarizing plate 1 in Example 1 waschanged to the polarizing plate 2 manufactured in Manufacturing Example2.

After that, a liquid crystal display device of Example 5 wasmanufactured by the same method as that in Example 1 except that theoptical sheet member of Example 5 was used instead of the optical sheetmember of Example 1, and the light source of the backlight was changedto B-LED manufactured by Nichia Corporation (Royal Blue, a mainwavelength of 445 nm, and a half-value width of 20 nm) in themanufacturing of the liquid crystal display device of Example 1.

Example 6

An optical sheet member of Example 6 was manufactured by the same methodas that in Example 1 except that the polarizing plate 1 in Example 1 waschanged to the polarizing plate 3 manufactured in Manufacturing Example3.

After that, a liquid crystal display device of Example 6 wasmanufactured by the manufactured by the same method as that in Example 1except that the optical sheet member of Example 6 was used instead ofthe optical sheet member of Example 1, and the light source of thebacklight was changed to B-LED manufactured by Nichia Corporation (RoyalBlue, a main wavelength of 445 nm, and a half-value width of 20 nm) inthe manufacturing of the liquid crystal display device of Example 1.

Example 7

<Preparation of Quantum Dot Material Dispersed Adhesive Material>

Quantum dot materials which emitted fluorescent light of green lighthaving a center wavelength of 560 nm and a half-value width of 40 nm andred light having a center wavelength of 610 nm and a half-value width of40 nm when blue light of a blue light emitting diode was incidentthereon were dispersed in an adhesive material prepared with referenceto JP2003-13029A, and thus a quantum dot material dispersed adhesivematerial was prepared.

<Manufacturing of Optical Sheet Member and Liquid Crystal DisplayDevice>

The retardation film prepared in Manufacturing Example 1 was bonded toone surface of the polarizer prepared in Manufacturing Example 1 by thesame method as that in Manufacturing Example 1, and the B narrowband λ/4plate prepared in Example 1 was bonded to the other surface of thepolarizer by using the quantum dot material dispersed adhesive materialprepared as described above. After that, a light reflecting layer formedby fixing a cholesteric liquid crystalline phase was formed on the Bnarrowband λ/4 plate by the same method as that in Example 1, and thusan optical sheet member of Example 7 was manufactured.

After that, a liquid crystal display device of Example 7 wasmanufactured by the same method as that in Example 1 except that theoptical sheet member of Example 7 was used instead of the optical sheetmember of Example 1, and the light source of the backlight was changedto B-LED manufactured by Nichia Corporation (Royal Blue, a mainwavelength of 445 nm, and a half-value width of 20 nm) in themanufacturing of the liquid crystal display device of Example 1.

Example 8

<Preparation of Quantum Rod Dispersed CA>

In manufacturing of a cellulose acylate film disclosed in Example 1 ofJP2011-121327A, quantum rods which emitted fluorescent light of greenlight having a center wavelength of 560 nm and a half-value width of 40nm and red light having a center wavelength of 640 nm and a half-valuewidth of 40 nm when blue light of a blue light emitting diode wasincident thereon was dispersed in cellulose acylate in the amount of 0.1mass %, and thus a quantum rod dispersed and stretched cellulose acylatefilm (in the following tables, referred to as quantum rod dispersed andstretched CA) was prepared. In this quantum rod dispersed and stretchedcellulose acylate film, when light having a polarization degree of 99.9%was incident on the quantum rod dispersed and stretched celluloseacylate film, the polarization degree of the fluorescent light emittedfrom the quantum rod dispersed and stretched cellulose acylate film was80%. In addition, it was confirmed that the polarization degree of thefluorescent light emitted from the quantum rod dispersed and stretchedcellulose acylate film was enhanced according to stretching ratio UP.

<Manufacturing of Polarizing Plate 4>

The retardation film prepared in Manufacturing Example 1 was bonded toone surface of the polarizer prepared in Manufacturing Example 1 by thesame method as that in Manufacturing Example 1, and the quantum roddispersed and stretched cellulose acylate film prepared as describedabove was bonded to the other surface of the polarizer by the samemethod as that in Manufacturing Example 1, and thus a polarizing plate 4was manufactured.

<Manufacturing of Optical Sheet Member and Liquid Crystal DisplayDevice>

An optical sheet member of Example 8 was manufactured by the same methodas that in Example 1 except that the polarizing plate 4 manufactured asdescribed above was used instead of the polarizing plate 1 in Example 1.

After that, a liquid crystal display device of Example 8 wasmanufactured by the manufactured by the same method as that in Example 1except that the optical sheet member of Example 8 was used instead ofthe optical sheet member of Example 1, and the light source of thebacklight was changed to B-LED manufactured by Nichia Corporation (RoyalBlue, a main wavelength of 445 nm, and a half-value width of 20 nm) inthe manufacturing of the liquid crystal display device of Example 1.

Example 9

<Formation of Broadband λ/4 Plate>

As described in “0020” to “0033” of JP2003-262727A, a broadband λ/4plate was prepared. The broadband λ/4 plate was obtained by applying aliquid crystal material of two layers onto a substrate, and byperforming polymerization with respect to the liquid crystal material,and then by peeling off the liquid crystal material from the substrate.

In the obtained broadband λ/4 plate, Re(450) was 110 nm, Re(550) was 135nm, Re(630) was 140 nm, and the film thickness was 1.6 μm.

<Manufacturing of Optical Sheet Member and Liquid Crystal DisplayDevice>

An optical sheet member of Example 9 was manufactured by the same methodas that in Example 1 except that the broadband λ/4 plate manufactured asdescribed above was used instead of the B narrowband λ/4 plate, and thetotal thickness of the brightness enhancement film was changed as shownin Table 2 described below by changing the thickness of the λ/4 plate inExample 1.

After that, a liquid crystal display device of Example 9 wasmanufactured by the manufactured by the same method as that in Example 1except that the optical sheet member of Example 9 was used instead ofthe optical sheet member of Example 1, and the light source of thebacklight was changed to B-LED manufactured by Nichia Corporation (RoyalBlue, a main wavelength of 445 nm, and a half-value width of 20 nm) inthe manufacturing of the liquid crystal display device of Example 1.

Example 10

An optical sheet member and a liquid crystal display device of Example10 were manufactured by the same method as that in Example 1 except thatthe broadband λ/4 plate manufactured in Example 9 was used instead ofthe B narrowband λ/4 plate, and the adhesive agent for adhesion betweenthe reflection polarizer and the polarizing plate was changed to anadhesive agent having a refractive index of 1.55 in Example 1.

Example 11

The quantum dot sheet manufactured in Example 1 was bonded to thepolarizing plate 1 manufactured in Manufacturing Example 1 by the samemethod as that in Example 1. After that, a B narrowband dielectricmultilayer film 1 prepared by the following method was bonded to thequantum dot sheet by using the same adhesive agent as that of Example 1,and thus an optical sheet member of Example 11 was manufactured.

The B narrowband dielectric multilayer film 1 was manufactured such thatthe reflection center wavelength of the peak of the maximum reflectivityin a wavelength range corresponding to blue light was 465 nm, and thehalf-value width was 30 nm by changing the total thickness of thebrightness enhancement film as shown in Table 2 described below withreference to IDW/AD '12, pp.985 to 988 (2012).

A liquid crystal display device of Example 11 was manufactured by thesame method as that in Example 1 except that the optical sheet member ofExample 11 was used instead of the optical sheet member of Example 1 inthe manufacturing of the liquid crystal display device of Example 1.

Example 12

The quantum rod dispersed and stretched cellulose acylate film preparedin Example 8 was bonded to the polarizing plate 2 manufactured inManufacturing Example 2 by using the same adhesive agent as that ofExample 1. After that, the B narrowband dielectric multilayer film 1manufactured in Example 11 was bonded to the quantum rod dispersed andstretched cellulose acylate film by using the same adhesive agent asthat of Example 1, and thus an optical sheet member of Example 12 wasmanufactured.

A liquid crystal display device of Example 12 was manufactured by thesame method as that in Example 1 except that the optical sheet member ofExample 12 was used instead of the optical sheet member of Example 1 inthe manufacturing of the liquid crystal display device of Example 1.

Example 13

The quantum rod dispersed and stretched cellulose acylate film preparedin Example 8 was bonded to the polarizing plate 3 manufactured inManufacturing Example 3 by using the same adhesive agent as that ofExample 1. After that, the B narrowband dielectric multilayer film 1manufactured in Example 11 was bonded to the quantum rod dispersed andstretched cellulose acylate film by using the same adhesive agent asthat of Example 1, and thus an optical sheet member of Example 13 wasmanufactured.

A liquid crystal display device of Example 13 was manufactured by thesame method as that in Example 1 except that the optical sheet member ofExample 13 was used instead of the optical sheet member of Example 1 inthe manufacturing of the liquid crystal display device of Example 1.

Example 14

The B narrowband dielectric multilayer film 1 manufactured in Example 11was bonded to the polarizing plate 4 manufactured in Example 8 by usingthe same adhesive agent as that of Example 1, and thus an optical sheetmember of Example 14 was manufactured.

A liquid crystal display device of Example 14 was manufactured by thesame method as that in Example 1 except that the optical sheet member ofExample 14 was used instead of the optical sheet member of Example 1 inthe manufacturing of the liquid crystal display device of Example 1.

Example 15

The quantum dot sheet (the quantum dot material (B,G,R)) obtained inExample 2 and the polarizing plate 1 manufactured in ManufacturingExample 1 were bonded to each other by using an acrylic adhesive agenthaving a refractive index of 1.47. After that, an UV narrowbanddielectric multilayer film 2 prepared by the following method was bondedto the quantum dot sheet by using the same adhesive agent as that ofExample 1, and thus an optical sheet member of Example 15 wasmanufactured.

The UV narrowband dielectric multilayer film 2 was manufactured suchthat the reflection center wavelength of the peak of the maximumreflectivity in a wavelength range corresponding to UV light was 385 nm,and the half-value width was 30 nm by changing the total thickness ofthe brightness enhancement film as shown in Table 2 described below withreference to IDW/AD '12, pp.985 to 988 (2012).

A liquid crystal display device of Example 15 was manufactured by thesame method as that in Example 2 except that was the optical sheetmember of Example 15 was used instead of the optical sheet member ofExample 2, and the light source of the backlight was changed to UV-LEDmanufactured by Nichia Corporation (NC4U134A, a main wavelength of 385nm, and a half-value width of 10 nm) in the manufacturing of the liquidcrystal display device of Example 2.

Example 16

An optical sheet member and a liquid crystal display device of Example16 were manufactured by the same method as that in Example 1 except thatthe center wavelength of the peak of the maximum reflectivity of thelight reflecting layer was set to 435 nm, and the half-value width wasset to 70 nm by changing the added amount of the chiral agent of thereflection polarizer in Example 1.

Example 17

A quantum rod 1 which emitted fluorescent light of green light having acenter wavelength of 540 nm and a half-value width of 40 nm and aquantum rod 2 which emitted fluorescent light of red light having acenter wavelength of 645 nm and a half-value width of 30 nm when bluelight of a blue light emitting diode was incident thereon were formed asthe optical conversion member with reference to U.S. Pat. No. 7303628B,an article (Peng, X. G; Manna, L.; Yang, W. D.; Wickham, j.; Scher, E.;Kadavanich, A.; Alivisatos, A. P.Nature 2000, 404, 59-61), and anarticle (Manna, L.; Scher, E. C.; Alivisatos, A. P. j. Am. Chem. Soc.2000, 122, 12700-12706). The quantum rods 1 and 2 were in the shape of arectangular parallelepiped, and the average length of the major axis ofthe quantum rod was 30 nm. Furthermore, the average length of the majoraxis of the quantum rod was confirmed by using a transmission typeelectron microscope.

Next, a quantum rod dispersed PVA sheet in which the quantum rods weredispersed was prepared by the following method.

A sheet of an isophthalic acid copolymerized polyethylene terephthalatein which an isophthalic acid was copolymerized in the amount of 6 mol %(hereinafter, referred to as “amorphous PET”) was prepared as asubstrate. The glass transition temperature of the amorphous PET was 75°C. A laminated body formed of the amorphous PET substrate and a quantumrod alignment layer was prepared as follows. Here, the quantum rodalignment layer included the quantum rods 1 and 2 which were prepared byusing polyvinyl alcohol (hereinafter, referred to as “PVA”) as a matrix.In addition, the glass transition temperature of the PVA was 80° C.

4% concentration to 5% concentration of a PVA powder having a degree ofpolymerization of greater than or equal to 1,000 and a degree ofsaponification of greater than or equal to 99%, and 1% concentration ofeach of the quantum rods 1 and 2 prepared as described above weredissolved in water, and thus an aqueous solution of quantumrod-containing PVA was prepared. In addition, an amorphous PET substratehaving a thickness of 200 μm was prepared. Next, the amorphous PETsubstrate having a thickness of 200 μm was coated with the aqueoussolution of the quantum rod-containing PVA, and was dried at atemperature of 50° C. to 60° C., and thus a quantum rod-containing PVAlayer having a thickness of 25 μm was formed on the amorphous PETsubstrate. A laminated body of the amorphous PET and the quantumrod-containing PVA was referred to as a quantum rod dispersed PVA sheet.

In the prepared quantum rod dispersed PVA sheet, the polarization degreeof fluorescent light which was emitted from the quantum rod dispersedPVA sheet when light having a polarization degree of 99.9% was incidentthereon was 80%.

A liquid crystal display device of Example 17 was manufactured by thesame method as that in Example 8 except that the quantum rod dispersedPVA sheet formed as described above was used instead of the quantum roddispersed and stretched cellulose acylate film in Example 8. An opticalsheet member of Example 17 was manufactured by using the quantum roddispersed PVA sheet described above and the same configuration as thatof Example 8.

A liquid crystal display device (a product name of KDL-46W900A,manufactured by Sony Corporation) including a commercially availablequantum dot type backlight was used, the optical sheet member of Example17 was used as the backlight side polarizing plate, the TV describedabove was disassembled, a quantum dot (a glass enclosed bar type quantumdot) was extracted, and the quantum dot type backlight was changed to aB narrowband (450 nm) backlight unit, and thus a liquid crystal displaydevice of Example 17 was manufactured.

The B narrowband backlight unit included a blue light emitting diode(Blue, a main wavelength of 450 nm, and a half-value width of 20 nm) asa light source.

Example 18

The quantum rod dispersed PVA sheet prepared in Example 17 was bonded tothe polarizing plate 2 manufactured in Manufacturing Example 2 by usingthe same adhesive agent as that of Example 1. After that, the Bnarrowband cholesteric reflection polarizer manufactured in Example 8was bonded to the quantum rod dispersed PVA sheet by using the sameadhesive agent as that of Example 1, and thus an optical sheet member ofExample 18 was manufactured.

In the manufacturing of the liquid crystal display device of Example 2,a liquid crystal display device of Example 18 was manufactured by usingthe optical sheet member of Example 18 instead of the optical sheetmember of Example 2, by using the polarizing plate 2 manufactured inManufacturing Example 2 as the backlight side polarizing plate, and bysetting a broadband dielectric multilayer film (a product name of DBEF,manufactured by 3M Company) incorporated in a liquid crystal displaydevice (a product name of KDL-46W900A, manufactured by Sony Corporation)between the optical member sheet and the polarizing plate 2.

Example 19

A quantum rod 1 which emitted fluorescent light of green light having acenter wavelength of 540 nm and a half-value width of 40 nm, a quantumrod 2 which emitted fluorescent light of red light having a centerwavelength of 645 nm and a half-value width of 30 nm, and a quantum rod3 which emitted fluorescent light of blue light having a centerwavelength of 450 nm and a half-value width of 20 nm when UV light of anUV light emitting diode was incident thereon were formed as the opticalconversion member. The quantum rods 1, 2, and 3 were in the shape of arectangular parallelepiped, and the average length of the major axis ofthe quantum rod was 30 nm. Furthermore, the average length of the majoraxis of the quantum rod was confirmed by using a transmission typeelectron microscope.

Next, a quantum rod dispersed PVA sheet in which the quantum rods weredispersed was prepared by the following method.

A sheet of an isophthalic acid copolymerized polyethylene terephthalatein which an isophthalic acid was copolymerized in the amount of 6 mol %(hereinafter, referred to as “amorphous PET”) was prepared as asubstrate. The glass transition temperature of the amorphous PET was 75°C. A laminated body formed of the amorphous PET substrate and a quantumrod alignment layer was prepared as follows. Here, the quantum rodalignment layer included the quantum rods 1, 2, and 3 which wereprepared by using polyvinyl alcohol (hereinafter, referred to as “PVA”)as a matrix. In addition, the glass transition temperature of the PVAwas 80° C.

4% concentration to 5% concentration of a PVA powder having a degree ofpolymerization of greater than or equal to 1,000 and a degree ofsaponification of greater than or equal to 99%, and 1% concentration ofeach of the quantum rods 1 and 2 prepared as described above weredissolved in water, and thus an aqueous solution of quantumrod-containing PVA was prepared. In addition, an amorphous PET substratehaving a thickness of 200 μm was prepared. Next, the amorphous PETsubstrate having a thickness of 200 μm was coated with the aqueoussolution of the quantum rod-containing PVA, and was dried at atemperature of 50° C. to 60° C., and thus a quantum rod-containing PVAlayer having a thickness of 25 μm was formed on the amorphous PETsubstrate. A laminated body of the amorphous PET and the quantumrod-containing PVA was referred to as a quantum rod dispersed PVA sheet.

The quantum rod dispersed PVA sheet described above was bonded to thepolarizing plate 3 manufactured in Manufacturing Example 3 by the sameadhesive agent as that of Example 1. After that, the brightnessenhancement film including the UV narrowband λ/4 plate manufactured inExample 2 and an UV narrowband cholesteric reflection polarizer wasbonded to the quantum rod dispersed PVA sheet by using the same adhesiveagent as that of Example 1, and thus an optical sheet member of Example19 was manufactured.

A liquid crystal display device of Example 19 was manufactured by thesame method as that in Example 18 except that a broadband dielectricmultilayer film (a product name of APF, manufactured by 3M Company) wasused instead of the polarizing plate 2, and the UV light source used inExample 15 was used as the light source in the manufacturing of theliquid crystal display device of Example 18.

Example 20

The quantum rod dispersed PVA sheet prepared in Example 17 was bonded tothe polarizing plate 1 manufactured in Manufacturing Example 1 by usingthe same adhesive agent as that of Example 1. After that, the Bnarrowband cholesteric reflection polarizer manufactured in Example 8was bonded to the quantum rod dispersed PVA sheet by using the sameadhesive agent as that of Example 1, and thus an optical sheet member ofExample 20 was manufactured.

In the manufacturing of the liquid crystal display device of Example 17,a liquid crystal display device of Example 20 was manufactured by usingthe polarizing plate 1 which was manufactured by using the optical sheetmember of Example 20 instead of the optical sheet member of Example 17as the backlight side polarizing plate in Manufacturing Example 1, andby setting a B narrowband cholesteric and λ/4 layer which was preparedby the same method as that in Example 1 between the optical member sheetand the polarizing plate 1.

Example 21

The quantum rod dispersed PVA sheet prepared in Example 17 was bonded tothe polarizing plate 2 manufactured in Manufacturing Example 2 by usingthe same adhesive agent as that of Example 1. After that, the Bnarrowband cholesteric reflection polarizer manufactured in Example 8was bonded to the quantum rod dispersed PVA sheet by using the sameadhesive agent as that of Example 1, and thus an optical sheet member ofExample 21 was manufactured.

In the manufacturing of the liquid crystal display device of Example 8,a liquid crystal display device of Example 21 was manufactured by usingthe polarizing plate 2 which was manufactured by using the optical sheetmember of Example 21 instead of the optical sheet member of Example 8 asthe backlight side polarizing plate in Manufacturing Example 2, and bysetting a B narrowband dielectric multilayer film which was prepared bythe same method as that in Example 11 between the optical member sheetand the polarizing plate 2.

Comparative Example 1

A commercially available liquid crystal display device (a product nameof TH-L42D2, manufactured by Panasonic Corporation) was disassembled,the polarizing plate 1 manufactured in Manufacturing Example 1 was usedas the backlight side polarizing plate, and a dielectric multilayer film(a product name of DBEF, manufactured by 3M Company) was separatelyarranged between the backlight side polarizing plate and the backlightunit without disposing an adhesive agent, and thus a liquid crystaldisplay device of Comparative Example 1 was manufactured.

The dielectric multilayer film (a product name of DBEF) had reflectivityof a flat peak with respect to an approximately constant wavelength in450 nm to 550 nm to 630 nm of a blue region to a green region to a redregion.

In the backlight light source of this liquid crystal display device, thelight emitting peak wavelength of the blue light was 450 nm. In a greenregion to a red region, the number of light emitting peaks was one, thepeak wavelength was 550 nm, and the half-value width was 100 nm.

Comparative Example 2

A broadband λ/4 plate prepared by the same method as that in Example 9and the polarizing plate 1 manufactured as described above were bondedto each other by using an acrylic adhesive agent having a refractiveindex of 1.47.

An optical sheet member of Comparative Example 2 was manufactured by thesame method as that in Example 1 except that five layers formed byfixing broadband cholesteric liquid crystalline phases were laminatedinstead of the first light reflecting layer, the second light reflectinglayer, and the third light reflecting layer, and the total thickness ofthe brightness enhancement film was changed as shown in Table 2described below in Example 1.

In addition, a liquid crystal display device of Comparative Example 2was manufactured by the same method as that in Example 1 except that theoptical sheet member of Comparative Example 2 was used instead of theoptical sheet member of Example 1, and the same backlight unit as thatof Comparative Example 1 was used without changing the backlight unit inthe manufacturing of the liquid crystal display device of Example 1.

[Evaluation]

The optical sheet members and the liquid crystal display devices of therespective examples and comparative examples were evaluated according tothe following criteria. Furthermore, in Examples 1 to 10 and 16 to 21,the evaluation was based on Comparative Example 2, and in Examples 11 to15, the evaluation was based on Comparative Example 1.

(1) Front Brightness

Front brightness of the liquid crystal display device was measured byusing a method disclosed in “0180” of JP2009-93166A. The results thereofwere evaluated on the basis of the following criteria.

5: Excellent when the front brightness is greater than the frontbrightness of the liquid crystal display device of Comparative Example 1or 2 by greater than or equal to 30%

4: Excellent when the front brightness is greater than the frontbrightness of the liquid crystal display device of Comparative Example 1or 2 by greater than or equal to 20% and less than 30%

3: Excellent when the front brightness is greater than the frontbrightness of the liquid crystal display device of Comparative Example 1or 2 by greater than or equal to 10% and less than 20%

2: The front brightness is equal to of less than the front brightness ofthe liquid crystal display device of Comparative Example 1 or 2.

(2) Front Contrast

Front contrast of the liquid crystal display device was measured byusing a method disclosed in “0180” of JP2009-93166A. The results thereofwere evaluated on the basis of the following criteria.

4: Excellent when the front contrast is greater than the front contrastof the liquid crystal display device of Comparative Example 1 or 2 bygreater than or equal to 20%

3: Excellent when the front contrast is greater than the front contrastof the liquid crystal display device of Comparative Example 1 or 2 bygreater than or equal to 10% and less than 20%

2: The front contrast is equal to or less than the front contrast of theliquid crystal display device of Comparative Example 1 or 2.

(3) Color Reproducing Region

A color reproducing region of the liquid crystal display device wasmeasured by using a method disclosed in “0066” of JP2012-3073A. Theresults thereof were evaluated on the basis of the following criteria.

4: Excellent when the NTSC ratio is greater than the NTSC ratio of theliquid crystal display device of Comparative Example 1 or 2 by greaterthan or equal to 20%

3: Excellent when the NTSC ratio is greater than the NTSC ratio of theliquid crystal display device of Comparative Example 1 or 2 by greaterthan or equal to 10% and less than 20%

2: The NTSC ratio is equal to or less than the NTSC ratio of the liquidcrystal display device of Comparative Example 1 or 2.

(4) Color Unevenness in Inclined Azimuth

Color unevenness of the liquid crystal display device in an inclinedazimuth was measured by a method disclosed in JP2008-145868A. Theresults thereof were evaluated on the basis of the following criteria.

5: Excellent when the color unevenness is greater than the colorunevenness of the liquid crystal display device of Comparative Example 1or 2 in the inclined azimuth by greater than or equal to 30%

4: Excellent when the color unevenness is greater than the colorunevenness of the liquid crystal display device of Comparative Example 1or 2 in the inclined azimuth by greater than or equal to 20% and lessthan 30%

3: Excellent when the color unevenness is greater than the colorunevenness of the liquid crystal display device of Comparative Example 1or 2 in the inclined azimuth by greater than or equal to 10% and lessthan 20%

2: Excellent when the color unevenness is greater than the colorunevenness of the liquid crystal display device of Comparative Example 1or 2 in the inclined azimuth by less than 10%

1: The color unevenness is equal to or less than the color unevenness ofthe liquid crystal display device of Comparative Example 1 or 2 in theinclined azimuth.

TABLE 1 Comparative Comparative Example Example Example 1 Example 2 1-AExample 1 2-A Example 2 Example 3 Example 4 Example 5 Example 6 Example7 Liquid Polarizing Polarizer Present Present Present Present PresentPresent Present Present Present Present Present Crystal Plate PolarizingTAC Film TAC Film TAC Film TAC Film TAC Film TAC Film TAC Film TAC FilmAcrylic Film COP Absent (Pol Display Plate Direct Device ProtectiveBonding) Film Optical Fluorescent Absent Absent Quantum Quantum QuantumQuantum Quantum Quantum Quantum Quantum Quantum Dot Conversion Layer DotDot Dot Dot Dot Dot Dot Dot Material Member Material Material MaterialMaterial Material Material Material Material Material (G, R) (G, R) (G,R) (B, G, R) (B, G, R) (G, R) (B, G, R) (G, R) (G, R) Dispersed AdhesiveMaterial Brightness Between Absent Broadband Absent Narrowband AbsentNarrowband Narrowband Narrowband Narrowband Narrowband NarrowbandEnhancement Polarizing (Air λ/4 (Air λ/4 (Air λ/4 λ/4 λ/4 λ/4 λ/4 λ/4Film Plate Layer) (Integrated Layer) (Integrated Layer) (Integrated(Integrated (Integrated (Integrated (Integrated (Integrated Protectivewith with with with with with with with Film and Polarizing PolarizingPolarizing Polarizing Polarizing Polarizing Polarizing PolarizingFluorescent Plate Plate Plate Plate Plate Plate Plate Plate Layer/Protective Protective Protective Protective Protective ProtectiveProtective Protective Reflection Film and Film and Film and Film andFilm and Film and Film and Film and Polarizer Fluorescent FluorescentFluorescent Fluorescent Fluorescent Fluorescent Fluorescent FluorescentLayer/ Layer/ Layer/ Layer/ Layer/ Layer/ Layer/ Layer/ ReflectionReflection Reflection Reflection Reflection Reflection ReflectionReflection Polarizer Polarizer Polarizer Polarizer Polarizer PolarizerPolarizer Polarizer through through through through through throughthrough through Adhesive Adhesive Adhesive Adhesive Adhesive AdhesiveAdhesive Adhesive Agent) Agent) Agent) Agent) Agent) Agent) Agent)Agent) Difference in 1.57 0.1 1.57 (Air 0.1 1.57 (Air 0.1 0.1 0.1 0.10.1 0.1 Average Layer Layer Refractive Present) Present) Index betweenReflection Polarizer and Material Thereon (Adhesive Material or Air)Reflection DBEF of Five One B One B One UV One UV One B One UV One B OneB One B Polarizer Related Art Broadband Narrowband Narrowband NarrowbandNarrowband Narrowband Narrowband Narrowband Narrowband NarrowbandCholesteric Cholesteric Cholesteric Cholesteric Cholesteric CholestericCholesteric Cholesteric Cholesteric Cholesteric Layers Layer Layer LayerLayer Layer Layer Layer Layer Layer (Selective (Selective (Selective(Selective (Selective (Selective (Selective (Selective (SelectiveReflection Reflection Reflection Reflection Reflection ReflectionReflection Reflection Reflection at Light at Light at Light at Light atLight at Light at Light at Light at Light Source Source Source SourceSource Source Source Source Source Wavelength Wavelength WavelengthWavelength Wavelength Wavelength Wavelength Wavelength Wavelength of λb)of λb) of λb) of λb) of λb) of λb) of λb) of λb) of λb) Center — 430,490, 445 445 385 385 445 385 445 445 465 Wavelength 550, 610, (nm) 670Total 25 13 2.5 2.5 2 2 3 2 2.5 2.5 2.5 Thickness of BrightnessEnhancement Film (μm) Backlight BLU Including LED_BKL LED_BKL B-LEDB-LED UV-LED UV-LED B-LED UV-LED B-LED B-LED B-LED LED Light of ofSource (Light Related Related Guide Plate, Art Art Diffusion Plate,Condensing Prism, and the like) Light Source 450 450 450 465 365 365 445385 445 445 445 Wavelength λb (nm) Perfor- Front Brightness 2 2 3 4 4 44 4 4 4 4 mance Front Contrast 2 2 3 3 3 3 3 3 3 3 4 Color ReproducingRegion 2 2 4 4 4 4 4 4 4 4 4 Color Unevenness in 1 1 3 3 4 4 3 4 3 3 3Inclined Azimuth

TABLE 2 Example Example Example Example Example Example Example Example8 9 10 11 12 13 14 15 Liquid Crystal Polarizing Plate Polarizer PresentPresent Present Present Present Present Present Present Display DevicePolarizing Plate Absent TAC Film TAC Film TAC Film Acrylic COP AbsentTAC Film Protective Film (Pol Direct Film (Pol Direct Bonding) Bonding)Optical Conversion Fluorescent Quantum Dot Quantum Dot Quantum DotQuantum Dot Quantum Dot Quantum Dot Quantum Dot Quantum Dot MemberMaterial (G, R) Material Material Material (G, R) (G, R) (G, R) MaterialDispersed and (G, R) (G, R) (G, R) Dispersed and Dispersed and Dispersedand (B, G, R) Stretched CA Stretched CA Stretched CA Stretched CABrightness Between Polarizing Narrowband λ/4 Broadband λ/4 Broadband λ/4Only Only Only Only Only Enhancement Plate Protective (Integrated with(Integrated with (Integrated with Adhesive Adhesive Adhesive AdhesiveAdhesive Film Film and Fluorescent Polarizing Plate Polarizing PlatePolarizing Plate Material Material Material Material MaterialLayer/Reflection Protective Film Protective Film Protective FilmPolarizer and Fluorescent and Fluorescent and FluorescentLayer/Reflection Layer/Reflection Layer/Reflection Polarizer throughPolarizer through Polarizer through Adhesive Agent) Adhesive Agent)Adhesive Agent) Difference in Average 0.1 0.1 0.02 0.1 0.1 0.1 0.1 0.1Refractive Index between Reflection Polarizer and Material Thereon(Adhesive Material or Air) Reflection Polarizer One B Narrowband One BNarrowband One B Narrowband B Narrowband B Narrowband B Narrowband BNarrowband UV Narrowband Cholesteric Cholesteric Cholesteric DielectricDielectric Dielectric Dielectric Dielectric Layer (Selective Layer(Selective Layer (Selective Multilayer Multilayer Multilayer MultilayerMultilayer Reflection at Reflection at Reflection at Film 1 Film 1 Film1 Film 1 Film 2 Light Source Light Source Light Source Wavelength of λb)Wavelength of λb) Wavelength of λb) Center Wavelength (nm) 465 465 465465 465 465 465 385 Total Thickness of 2.5 3.5 2.5 10 10 10 10 8Brightness Enhancement Film (μm) Backlight BLU Including B-LED B-LEDB-LED B-LED B-LED B-LED B-LED UV-LED LED Light Source (Light GuidePlate, Diffusion Plate, Condensing Prism, and the like) Light SourceWavelength 445 445 465 465 465 465 465 385 λb Perfor- Front Brightness 43 5 3 3 3 3 3 mance Front Contrast 4 3 3 3 4 4 4 4 Color ReproducingRegion 4 4 4 4 4 4 4 4 Color Unevenness in Inclined Azimuth 3 4 4 3 3 33 4 Example Example Example Example Example Example 16 17 18 19 20 21Liquid Crystal Polarizing Plate Polarizer Present Present PresentAddition of Absent Only Reflection Present Addition Present Addition ofDisplay Device Reflection Polarizer Polarizer (Dielectric of ReflectionReflection Polarizer (Dielectric Multilayer Multilayer BroadbandPolarizer (B Narrowband Broadband Reflection Reflection Polarizer)(λ/4 + One Dielectric Multilayer Polarizer) B Narrowband ReflectionPolarizer) Cholesteric Layer) Polarizing Plate TAC Film Acryl Acryl COPTAC Film Acryl Protective Film Optical Conversion Fluorescent QuantumDot Quantum Dot Quantum Dot Quantum Dot Quantum Dot Quantum Dot MemberMaterial Material (G, R) Material (G, R) Material (G, R) Material (B, G,R) Material (G, R) Material (G, R) Dispersed PVA Dispersed PVA DispersedPVA Dispersed PVA Dispersed PVA Brightness Between Polarizing Narrowbandλ/4 Narrowband λ/4 Narrowband λ/4 Narrowband λ/4 Narrowband λ/4Narrowband λ/4 Enhancement Plate Protective (Integrated with (Integratedwith (Integrated with (Integrated with (Integrated with (Integrated withFilm Film and Fluorescent Polarizing Plate Polarizing Plate PolarizingPlate Polarizing Plate Polarizing Plate Polarizing PlateLayer/Reflection Protective Film Protective Film Protective FilmProtective Film Protective Film Protective Film Polarizer andFluorescent and Fluorescent and Fluorescent and Fluorescent andFluorescent and Fluorescent Layer/Reflection Layer/ReflectionLayer/Reflection Layer/Reflection Layer/Reflection Layer/ReflectionPolarizer through Polarizer through Polarizer through Polarizer throughPolarizer through Polarizer through Adhesive Agent) Adhesive Agent)Adhesive Agent) Adhesive Agent) Adhesive Agent) Adhesive Agent)Difference in Average 0.1 0.1 0.1 0.1 0.1 0.1 Refractive Index betweenReflection Polarizer and Material Thereon (Adhesive Material or Air)Reflection Polarizer One B Narrowband One B Narrowband One B NarrowbandOne UV Narrowband One B Narrowband One B Narrowband CholestericCholesteric Cholesteric Cholesteric Cholesteric Cholesteric Layer(Selective Layer (Selective Layer (Selective Layer (Selective Layer(Selective Layer (Selective Reflection at Reflection at Reflection atReflection at Reflection at Reflection at Light Source Light SourceLight Source Light Source Light Source Light Source Wavelength of λb)Wavelength of λb) Wavelength of λb) Wavelength of λb) Wavelength of λb)Wavelength of λb) Center Wavelength (nm) 435 465 465 385 465 465 TotalThickness of 2.5 3 3 2 2.5 3 Brightness Enhancement Film (μm) BacklightBLU Including B-LED B-LED B-LED UV-LED B-LED B-LED LED Light Source(Light Guide Plate, Diffusion Plate, Condensing Prism, and the like)Light Source Wavelength 465 450 450 385 450 450 λb Perfor- FrontBrightness 3 5 5 5 5 5 mance Front Contrast 3 3 3 2 3 3 ColorReproducing Region 4 4 4 3 4 4 Color Unevenness in Inclined Azimuth 3 33 3 3 3

From Table 1 and Table 2 described above, it was found that, when theoptical sheet member of the present invention used as the backlight sidepolarizing plate was incorporated in the image display device using theB narrowband or UV narrowband backlight, all of the front brightness,the front contrast, and the color reproducing region were improved andthe color unevenness in the inclined azimuth was reduced.

In contrast, from Comparative Example 1, it was found that, when theoptical sheet member not within the scope of the present invention whichwas used as the backlight side polarizing plate and in which the knownDBEF of the related art was used as the reflection polarizer wasincorporated in the image display device using the LED of the relatedart as the backlight, all of the front brightness, the front contrast,and the color reproducing region were required to be enhanced and thecolor unevenness in the inclined azimuth was required to be reduced.

From Comparative Example 2, it was found that, when the optical sheetmember not within the scope of the present invention which was used asthe backlight side polarizing plate and in which the reflectionpolarizer formed by laminating the five layers formed by fixing thecholesteric liquid crystals having a broadband reflection peak was usedwas incorporated in the image display device using the B narrowbandbacklight, all of the front brightness, the front contrast, and thecolor reproducing region were required to be enhanced and the colorunevenness in the inclined azimuth was required to be reduced.

In addition, in order to further improve the front brightness of theliquid crystal display device using the optical sheet member of thepresent invention, it is preferable that one or more prism sheets areused in the backlight unit, and it is more preferable that two prismsheets are included. Further, it is found that it is particularlypreferable that the prism directions of the two prism sheets aresubstantially parallel to each other. The expression “the prismdirections of the two prism sheets are substantially parallel to eachother” indicates that an angle between the prisms of the two prismsheets is within ±5°.

As a result of intensive studies of the present inventors, it has beenfound that the front brightness is able to be higher when the prismdirections of the two prism sheets are parallel to each other ratherthan being vertical to each other in the brightness enhancement film ofthe present invention.

Furthermore, a wavelength selective filter for a blue color whichselectively transmitted light having a wavelength shorter than 460 nmwas disposed in the backlight unit of the liquid crystal display deviceof Example 1, and thus the same preferred evaluation results wereobtained.

EXPLANATION OF REFERENCES

1: backlight side polarizing plate

2: retardation film

3: polarizer (A)

3 ab: absorption axis direction of polarizer (A)

4: polarizing plate protective film

11: brightness enhancement film

12: λ/4 plate (C)

12 s 1: slow axis direction of λ/4 plate (C)

13: reflection polarizer (B)

14B: B narrowband layer formed by fixing cholesteric liquid crystallinephase

14UV: UV narrowband layer formed by fixing cholesteric liquidcrystalline phase

15B: B narrowband dielectric multilayer film

15UV: UVB narrowband dielectric multilayer film

16 a: optical conversion member (conversion from B to G and R)

16 b: optical conversion member (conversion from UV to B, G, and R)

17: linear polarization reflection polarizer

18: circular polarization reflection polarizer

20: adhesive layer (adhesive agent)

21: optical sheet member

31B: B narrowband backlight unit

31UV: UV narrowband backlight unit

41: thin layer transistor substrate

42: liquid crystal cell

43: color filter substrate

44: display side polarizing plate

51: image display device

What is claimed is:
 1. An optical sheet member, comprising: a polarizingplate including a polarizer (A); an optical conversion member (D); and abrightness enhancement film including a reflection polarizer (B),wherein the brightness enhancement film has a reflection centerwavelength in a wavelength range of 300 nm to 430 nm and a peak ofreflectivity having a half-value width of less than or equal to 100 nm,and the optical conversion member (D) converts a part or all of UV lightwhich is transmitted through the reflection polarizer (B) and isincident on the optical conversion member (D), and has an emissioncenter wavelength in the wavelength range of 300 nm to 430 nm and a peakof emission intensity having a half-value width of less than or equal to100 nm into blue light which has an emission center wavelength in awavelength range of 430 nm to 480 nm and a peak of emission intensityhaving a half-value width of less than or equal to 100 nm, green lightwhich has an emission center wavelength in a wavelength range of 500 nmto 600 nm and a peak of emission intensity having a half-value width ofless than or equal to 100 nm, and red light which has an emission centerwavelength in a wavelength range of 600 nm to 700 nm and a peak ofemission intensity having a half-value width of less than or equal to100 nm.
 2. The optical sheet member according to claim 1, wherein theoptical conversion member (D) converts a part or all of UV light whichis transmitted through the reflection polarizer (B) and is incident onthe optical conversion member (D), and has an emission center wavelengthin the wavelength range of 300 nm to 430 nm and a peak of emissionintensity having a half-value width of less than or equal to 100 nm intoblue light which has an emission center wavelength in the wavelengthrange of 430 nm to 480 nm and a peak of emission intensity having ahalf-value width of less than or equal to 100 nm, green light which hasan emission center wavelength in the wavelength range of 500 nm to 600nm and a peak of emission intensity having a half-value width of lessthan or equal to 100 nm, and red light which has an emission centerwavelength in a wavelength range of 600 nm to 650 nm and a peak ofemission intensity having a half-value width of less than or equal to100 nm.
 3. The optical sheet member according to claim 1, wherein thereflection polarizer (B) includes a first light reflecting layer whichhas a reflection center wavelength in the wavelength range of 300 nm to430 nm and a peak of reflectivity having a half-value width of less thanor equal to 100 nm, and is formed by fixing a cholesteric liquidcrystalline phase, the brightness enhancement film includes a λ/4 plate(C) satisfying Expression (2) described below between the opticalconversion member (D) and the reflection polarizer (B),380 nm/4−60 nm<Re(380)<380 nm/4+60 nm, and  Expression (2) in Expression(2), Re(λ) represents retardation in an in-plane direction at awavelength of λ nm, and unit is nm.
 4. The optical sheet memberaccording to claim 1, wherein the reflection polarizer (B) includes thefirst light reflecting layer which has a reflection center wavelength inthe wavelength range of 300 nm to 430 nm and a peak of reflectivityhaving a half-value width of less than or equal to 100 nm, and is formedby fixing the cholesteric liquid crystalline phase, the brightnessenhancement film includes a λ/4 plate (C) satisfying Expression (2')described below between the optical conversion member (D) and thereflection polarizer (B),380 nm/4−25 nm<Re(380)<380 nm/4+25 nm, and  Expression (2′) inExpression (2′), Re(λ) represents retardation in an in-plane directionat a wavelength of λ nm, and unit is nm.
 5. The optical sheet memberaccording to claim 1, wherein the reflection polarizer (B) is adielectric multilayer film which has a reflection center wavelength inthe wavelength range of 300 nm to 430 nm and a peak of reflectivityhaving a half-value width of less than or equal to 100 nm.
 6. Theoptical sheet member according to claim 1, wherein the opticalconversion member (D) and the reflection polarizer (B) are laminated indirect contact with each other or through an adhesive layer.
 7. Theoptical sheet member according to claim 1, wherein a difference inrefractive indexes between the reflection polarizer (B) and a layer indirect contact with the reflection polarizer (B) on the polarizing plateside is less than or equal to 0.15.
 8. The optical sheet memberaccording to claim 1, wherein a film thickness of the brightnessenhancement film is 3 μm to 10 μm.
 9. The optical sheet member accordingto claim 1, wherein the optical conversion member (D) includes afluorescent material emitting the blue light, the green light, and thered light when light having an emission center wavelength in thewavelength range of 300 nm to 430 nm and a peak of emission intensityhaving a half-value width of less than or equal to 100 nm is incidentthereon.
 10. The optical sheet member according to claim 9, wherein theoptical conversion member (D) is a thermoplastic film which is formed bybeing stretched after dispersing quantum dot sheets, quantum rods, orquantum dot materials, or an adhesive layer on which quantum rods orquantum dot materials are dispersed.
 11. The optical sheet memberaccording to claim 1, wherein the optical conversion member emitsfluorescent light holding at least a part of polarization properties ofan incidence ray.
 12. The optical sheet member according to claim 11,wherein in the optical conversion member, a polarization degree offluorescent light emitted from the optical conversion member is 10% to99% when light having a polarization degree of 99.9% is incident on theoptical conversion member.
 13. The optical sheet member according toclaim 1, wherein the optical conversion member includes a fluorescentmaterial in which light exited from the optical conversion memberincludes linear polarization light and circular polarization light. 14.The optical sheet member according to claim 1, wherein light exited fromthe optical conversion member includes the linear polarization light,and the polarizing plate further includes a linear polarizationreflection polarizer or further includes a linear polarizationreflection polarizer between the polarizing plate and the opticalconversion member.
 15. The optical sheet member according to claim 14,wherein the linear polarization reflection polarizer is a dielectricmultilayer film which reflects at least a part of light in a wavelengthrange of 300 nm to 500 nm.
 16. The optical sheet member according toclaim 14, wherein the linear polarization reflection polarizer is alinear polarization reflection polarizer including a λ/4 plate on bothsides of a light reflecting layer which is formed by fixing acholesteric liquid crystalline phase reflecting at least a part of lightin a wavelength range of 300 nm to 500 nm.
 17. The optical sheet memberaccording to claim 1, wherein light exited from the optical conversionmember includes the circular polarization light, and the polarizingplate further includes a circular polarization reflection polarizer orfurther includes a circular polarization reflection polarizer betweenthe polarizing plate and the optical conversion member.
 18. The opticalsheet member according to claim 17, wherein the circular polarizationreflection polarizer is a circular polarization reflection polarizerincluding a λ/4 plate on both sides of a dielectric multilayer filmwhich reflects at least a part of light in a wavelength range of 300 nmto 500 nm.
 19. The optical sheet member according to claim 18, whereinthe circular polarization reflection polarizer is a circularpolarization reflection polarizer including a light reflecting layerwhich is formed by fixing a cholesteric liquid crystalline phasereflecting at least a part of light in a wavelength range of 300 nm to500 nm and a λ/4 plate which is arranged between the light reflectinglayer and the polarizing plate.
 20. The optical sheet member accordingto claim 1, wherein the optical conversion member is pattern-formed ateach two or more types of fluorescent wavelengths.
 21. An image displaydevice, comprising: the optical sheet member according to claim 1; and abacklight unit, wherein the backlight unit includes a light sourceemitting UV light which has an emission center wavelength in thewavelength range of 300 nm to 430 nm and a peak of emission intensityhaving a half-value width of less than or equal to 100 nm, and thebacklight unit includes a reflection member performing conversion of apolarization state of light which is emitted from the light source andis reflected on the optical sheet member and reflection of the light ina rear portion of the light source.
 22. The image display deviceaccording to claim 21, wherein a difference between a wavelengthapplying a peak of emission intensity of UV light of the backlight unitand a wavelength applying a peak of reflectivity in the brightnessenhancement film is 5 nm to 70 nm.
 23. The image display deviceaccording to claim 21, further comprising: a liquid crystal cell. 24.The image display device according to claim 21, further comprising: athin layer transistor, wherein the thin layer transistor includes anoxide semiconductor layer having a carrier concentration of less than1×10¹⁴/cm³.